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 $233.40   5.651%   $246.5894   $246.59   $246.60   $246.60  
  Purchase #2 $132.86   10.869%   $147.3006   $147.30   $147.30   $147.30  
  Purchase #3 $129.97   6.472%   $138.3817   $138.38   $138.40   $138.40  
  Purchase #4 $88.43   6.424%   $94.1107   $94.11   $94.10   $94.10  
  Purchase #5 $212.83   8.238%   $230.3629   $230.36   $230.35   $230.40  
  Purchase #6 $232.33   11.835%   $259.8263   $259.83   $259.85   $259.80  
  Purchase #7 $229.52   6.446%   $244.3149   $244.31   $244.30   $244.30  
  7 purchase totals = $1,259.34       $1,360.8865   $1,360.88   $1,360.90   $1,360.90