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 $53.85   8.351%   $58.347   $58.35   $58.35   $58.30  
  Purchase #2 $246.97   11.833%   $276.194   $276.19   $276.20   $276.20  
  Purchase #3 $147.40   4.477%   $153.9991   $154.00   $154.00   $154.00  
  Purchase #4 $184.52   9.771%   $202.5494   $202.55   $202.55   $202.50  
  Purchase #5 $44.31   12.408%   $49.808   $49.81   $49.80   $49.80  
  Purchase #6 $138.31   5.362%   $145.7262   $145.73   $145.75   $145.70  
  Purchase #7 $113.88   6.116%   $120.8449   $120.84   $120.85   $120.80  
  7 purchase totals = $929.24       $1,007.4686   $1,007.47   $1,007.50   $1,007.30