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 $213.54   7.332%   $229.1968   $229.20   $229.20   $229.20  
  Purchase #2 $62.30   10.744%   $68.9935   $68.99   $69.00   $69.00  
  Purchase #3 $175.80   10.840%   $194.8567   $194.86   $194.85   $194.90  
  Purchase #4 $92.98   3.740%   $96.4575   $96.46   $96.45   $96.50  
  Purchase #5 $191.78   8.107%   $207.3276   $207.33   $207.35   $207.30  
  Purchase #6 $47.92   12.392%   $53.8582   $53.86   $53.85   $53.90  
  Purchase #7 $157.90   3.766%   $163.8465   $163.85   $163.85   $163.80  
  7 purchase totals = $942.22       $1,014.5368   $1,014.55   $1,014.55   $1,014.60