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 $177.68   13.180%   $201.0982   $201.10   $201.10   $201.10  
  Purchase #2 $55.65   12.668%   $62.6997   $62.70   $62.70   $62.70  
  Purchase #3 $50.56   5.154%   $53.1659   $53.17   $53.15   $53.20  
  Purchase #4 $48.74   11.244%   $54.2203   $54.22   $54.20   $54.20  
  Purchase #5 $116.79   6.629%   $124.532   $124.53   $124.55   $124.50  
  Purchase #6 $204.65   3.665%   $212.1504   $212.15   $212.15   $212.20  
  Purchase #7 $134.51   7.805%   $145.0085   $145.01   $145.00   $145.00  
  7 purchase totals = $788.58       $852.8750   $852.88   $852.85   $852.90