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 $65.86   9.487%   $72.1081   $72.11   $72.10   $72.10  
  Purchase #2 $152.74   9.322%   $166.9784   $166.98   $167.00   $167.00  
  Purchase #3 $79.29   9.775%   $87.0406   $87.04   $87.05   $87.00  
  Purchase #4 $227.52   4.491%   $237.7379   $237.74   $237.75   $237.70  
  Purchase #5 $46.29   6.235%   $49.1762   $49.18   $49.20   $49.20  
  Purchase #6 $181.75   7.169%   $194.7797   $194.78   $194.80   $194.80  
  Purchase #7 $221.92   6.242%   $235.7722   $235.77   $235.75   $235.80  
  7 purchase totals = $975.37       $1,043.5931   $1,043.60   $1,043.65   $1,043.60