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 $66.54   11.852%   $74.4263   $74.43   $74.45   $74.40  
  Purchase #2 $25.94   4.810%   $27.1877   $27.19   $27.20   $27.20  
  Purchase #3 $176.51   4.293%   $184.0876   $184.09   $184.10   $184.10  
  Purchase #4 $191.96   10.756%   $212.6072   $212.61   $212.60   $212.60  
  Purchase #5 $165.72   8.431%   $179.6919   $179.69   $179.70   $179.70  
  Purchase #6 $210.89   8.368%   $228.5373   $228.54   $228.55   $228.50  
  Purchase #7 $120.65   4.622%   $126.2264   $126.23   $126.25   $126.20  
  7 purchase totals = $958.21       $1,032.7644   $1,032.78   $1,032.85   $1,032.70