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 $59.75   8.860%   $65.0439   $65.04   $65.05   $65.00  
  Purchase #2 $150.61   8.386%   $163.2402   $163.24   $163.25   $163.20  
  Purchase #3 $216.75   13.796%   $246.6528   $246.65   $246.65   $246.70  
  Purchase #4 $131.49   8.404%   $142.5404   $142.54   $142.55   $142.50  
  Purchase #5 $12.80   9.234%   $13.982   $13.98   $14.00   $14.00  
  Purchase #6 $172.71   8.797%   $187.9033   $187.90   $187.90   $187.90  
  Purchase #7 $230.62   8.196%   $249.5216   $249.52   $249.50   $249.50  
  7 purchase totals = $974.73       $1,068.8842   $1,068.87   $1,068.90   $1,068.80