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 $233.50   12.270%   $262.1505   $262.15   $262.15   $262.20  
  Purchase #2 $95.45   6.374%   $101.534   $101.53   $101.55   $101.50  
  Purchase #3 $68.46   11.288%   $76.1878   $76.19   $76.20   $76.20  
  Purchase #4 $211.73   5.402%   $223.1677   $223.17   $223.15   $223.20  
  Purchase #5 $193.28   5.769%   $204.4303   $204.43   $204.45   $204.40  
  Purchase #6 $85.85   11.794%   $95.9751   $95.98   $96.00   $96.00  
  Purchase #7 $88.52   12.282%   $99.392   $99.39   $99.40   $99.40  
  7 purchase totals = $976.79       $1,062.8374   $1,062.84   $1,062.90   $1,062.90