Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $210.26   9.374%   $229.9698   $229.97   $229.95   $230.00  
  Purchase #2 $205.96   13.532%   $233.8305   $233.83   $233.85   $233.80  
  Purchase #3 $142.83   6.234%   $151.734   $151.73   $151.75   $151.70  
  Purchase #4 $231.26   4.107%   $240.7578   $240.76   $240.75   $240.80  
  Purchase #5 $166.58   13.278%   $188.6985   $188.70   $188.70   $188.70  
  Purchase #6 $155.98   7.431%   $167.5709   $167.57   $167.55   $167.60  
  Purchase #7 $233.71   8.722%   $254.0942   $254.09   $254.10   $254.10  
  7 purchase totals = $1,346.58       $1,466.6557   $1,466.65   $1,466.65   $1,466.70