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 $67.38   10.723%   $74.6052   $74.61   $74.60   $74.60  
  Purchase #2 $218.96   7.488%   $235.3557   $235.36   $235.35   $235.40  
  Purchase #3 $230.70   4.511%   $241.1069   $241.11   $241.10   $241.10  
  Purchase #4 $108.36   9.419%   $118.5664   $118.57   $118.55   $118.60  
  Purchase #5 $145.46   10.216%   $160.3202   $160.32   $160.30   $160.30  
  Purchase #6 $73.63   9.551%   $80.6624   $80.66   $80.65   $80.70  
  Purchase #7 $50.50   10.396%   $55.75   $55.75   $55.75   $55.80  
  7 purchase totals = $894.99       $966.3668   $966.38   $966.30   $966.50