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 $68.65   3.539%   $71.0795   $71.08   $71.10   $71.10  
  Purchase #2 $40.97   11.500%   $45.6816   $45.68   $45.70   $45.70  
  Purchase #3 $187.33   6.777%   $200.0254   $200.03   $200.05   $200.00  
  Purchase #4 $191.84   5.305%   $202.0171   $202.02   $202.00   $202.00  
  Purchase #5 $246.96   5.788%   $261.254   $261.25   $261.25   $261.30  
  Purchase #6 $232.65   8.543%   $252.5253   $252.53   $252.55   $252.50  
  Purchase #7 $26.74   9.327%   $29.234   $29.23   $29.25   $29.20  
  7 purchase totals = $995.14       $1,061.8169   $1,061.82   $1,061.90   $1,061.80