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 $60.70   3.751%   $62.9769   $62.98   $63.00   $63.00  
  Purchase #2 $161.44   12.495%   $181.6119   $181.61   $181.60   $181.60  
  Purchase #3 $82.61   6.602%   $88.0639   $88.06   $88.05   $88.10  
  Purchase #4 $147.67   9.398%   $161.548   $161.55   $161.55   $161.50  
  Purchase #5 $245.30   12.317%   $275.5136   $275.51   $275.50   $275.50  
  Purchase #6 $76.44   8.636%   $83.0414   $83.04   $83.05   $83.00  
  Purchase #7 $223.84   8.269%   $242.3493   $242.35   $242.35   $242.30  
  7 purchase totals = $998.00       $1,095.1050   $1,095.10   $1,095.10   $1,095.00