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 $47.47   9.842%   $52.142   $52.14   $52.15   $52.10  
  Purchase #2 $212.66   13.424%   $241.2075   $241.21   $241.20   $241.20  
  Purchase #3 $119.90   5.142%   $126.0653   $126.07   $126.05   $126.10  
  Purchase #4 $247.32   10.514%   $273.3232   $273.32   $273.30   $273.30  
  Purchase #5 $145.52   5.681%   $153.787   $153.79   $153.80   $153.80  
  Purchase #6 $126.79   13.634%   $144.0765   $144.08   $144.10   $144.10  
  Purchase #7 $58.81   7.824%   $63.4113   $63.41   $63.40   $63.40  
  7 purchase totals = $958.47       $1,054.0128   $1,054.02   $1,054.00   $1,054.00