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 $61.66   9.136%   $67.2933   $67.29   $67.30   $67.30  
  Purchase #2 $161.70   13.494%   $183.5198   $183.52   $183.50   $183.50  
  Purchase #3 $137.31   5.609%   $145.0117   $145.01   $145.00   $145.00  
  Purchase #4 $241.86   9.775%   $265.5018   $265.50   $265.50   $265.50  
  Purchase #5 $187.64   9.114%   $204.7415   $204.74   $204.75   $204.70  
  Purchase #6 $184.58   7.250%   $197.9621   $197.96   $197.95   $198.00  
  Purchase #7 $200.26   7.125%   $214.5285   $214.53   $214.55   $214.50  
  7 purchase totals = $1,175.01       $1,278.5587   $1,278.55   $1,278.55   $1,278.50