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 $216.92   8.312%   $234.9504   $234.95   $234.95   $235.00  
  Purchase #2 $172.80   4.817%   $181.1238   $181.12   $181.10   $181.10  
  Purchase #3 $23.74   4.655%   $24.8451   $24.85   $24.85   $24.80  
  Purchase #4 $212.83   9.230%   $232.4742   $232.47   $232.45   $232.50  
  Purchase #5 $30.67   3.221%   $31.6579   $31.66   $31.65   $31.70  
  Purchase #6 $106.31   4.149%   $110.7208   $110.72   $110.70   $110.70  
  Purchase #7 $236.65   6.799%   $252.7398   $252.74   $252.75   $252.70  
  7 purchase totals = $999.92       $1,068.5120   $1,068.51   $1,068.45   $1,068.50