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 $54.26   11.605%   $60.5569   $60.56   $60.55   $60.60  
  Purchase #2 $118.55   5.543%   $125.1212   $125.12   $125.10   $125.10  
  Purchase #3 $126.87   6.364%   $134.944   $134.94   $134.95   $134.90  
  Purchase #4 $185.27   9.551%   $202.9651   $202.97   $202.95   $203.00  
  Purchase #5 $122.41   13.708%   $139.19   $139.19   $139.20   $139.20  
  Purchase #6 $141.31   7.640%   $152.1061   $152.11   $152.10   $152.10  
  Purchase #7 $204.95   3.472%   $212.0659   $212.07   $212.05   $212.10  
  7 purchase totals = $953.62       $1,026.9492   $1,026.96   $1,026.90   $1,027.00