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 $83.44   13.807%   $94.9606   $94.96   $94.95   $95.00  
  Purchase #2 $128.48   9.124%   $140.2025   $140.20   $140.20   $140.20  
  Purchase #3 $80.95   12.820%   $91.3278   $91.33   $91.35   $91.30  
  Purchase #4 $6.86   3.521%   $7.1015   $7.10   $7.10   $7.10  
  Purchase #5 $77.90   12.482%   $87.6235   $87.62   $87.60   $87.60  
  Purchase #6 $183.87   10.498%   $203.1727   $203.17   $203.15   $203.20  
  Purchase #7 $44.65   11.186%   $49.6445   $49.64   $49.65   $49.60  
  7 purchase totals = $606.15       $674.0331   $674.02   $674.00   $674.00