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 $196.51   7.837%   $211.9105   $211.91   $211.90   $211.90  
  Purchase #2 $116.35   11.470%   $129.6953   $129.70   $129.70   $129.70  
  Purchase #3 $95.26   6.614%   $101.5605   $101.56   $101.55   $101.60  
  Purchase #4 $218.65   13.141%   $247.3828   $247.38   $247.40   $247.40  
  Purchase #5 $192.41   13.291%   $217.9832   $217.98   $218.00   $218.00  
  Purchase #6 $199.52   7.349%   $214.1827   $214.18   $214.20   $214.20  
  Purchase #7 $46.44   12.476%   $52.2339   $52.23   $52.25   $52.20  
  7 purchase totals = $1,065.14       $1,174.9489   $1,174.94   $1,175.00   $1,175.00