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 $64.95   7.257%   $69.6634   $69.66   $69.65   $69.70  
  Purchase #2 $168.92   3.710%   $175.1869   $175.19   $175.20   $175.20  
  Purchase #3 $188.55   7.818%   $203.2908   $203.29   $203.30   $203.30  
  Purchase #4 $227.72   5.549%   $240.3562   $240.36   $240.35   $240.40  
  Purchase #5 $199.62   6.201%   $211.9984   $212.00   $212.00   $212.00  
  Purchase #6 $142.41   11.717%   $159.0962   $159.10   $159.10   $159.10  
  Purchase #7 $61.71   5.846%   $65.3176   $65.32   $65.30   $65.30  
  7 purchase totals = $1,053.88       $1,124.9095   $1,124.92   $1,124.90   $1,125.00