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 $97.52   3.542%   $100.9742   $100.97   $100.95   $101.00  
  Purchase #2 $18.82   9.380%   $20.5853   $20.59   $20.60   $20.60  
  Purchase #3 $180.58   3.251%   $186.4507   $186.45   $186.45   $186.50  
  Purchase #4 $243.71   10.680%   $269.7382   $269.74   $269.75   $269.70  
  Purchase #5 $139.84   6.774%   $149.3128   $149.31   $149.30   $149.30  
  Purchase #6 $227.87   6.456%   $242.5813   $242.58   $242.60   $242.60  
  Purchase #7 $60.27   6.725%   $64.3232   $64.32   $64.30   $64.30  
  7 purchase totals = $968.61       $1,033.9657   $1,033.96   $1,033.95   $1,034.00