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 $86.94   9.537%   $95.2315   $95.23   $95.25   $95.20  
  Purchase #2 $53.27   8.586%   $57.8438   $57.84   $57.85   $57.80  
  Purchase #3 $85.37   11.107%   $94.852   $94.85   $94.85   $94.90  
  Purchase #4 $120.52   12.335%   $135.3861   $135.39   $135.40   $135.40  
  Purchase #5 $193.73   12.556%   $218.0547   $218.05   $218.05   $218.10  
  Purchase #6 $184.54   4.210%   $192.3091   $192.31   $192.30   $192.30  
  Purchase #7 $223.47   12.563%   $251.5445   $251.54   $251.55   $251.50  
  7 purchase totals = $947.84       $1,045.2217   $1,045.21   $1,045.25   $1,045.20