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 $214.33   9.217%   $234.0848   $234.08   $234.10   $234.10  
  Purchase #2 $165.79   10.363%   $182.9708   $182.97   $182.95   $183.00  
  Purchase #3 $139.32   8.229%   $150.7846   $150.78   $150.80   $150.80  
  Purchase #4 $48.98   10.712%   $54.2267   $54.23   $54.25   $54.20  
  Purchase #5 $130.88   8.245%   $141.6711   $141.67   $141.65   $141.70  
  Purchase #6 $73.83   12.694%   $83.202   $83.20   $83.20   $83.20  
  Purchase #7 $193.65   7.228%   $207.647   $207.65   $207.65   $207.60  
  7 purchase totals = $966.78       $1,054.5870   $1,054.58   $1,054.60   $1,054.60