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 $197.42   8.827%   $214.8463   $214.85   $214.85   $214.80  
  Purchase #2 $101.84   4.607%   $106.5318   $106.53   $106.55   $106.50  
  Purchase #3 $54.86   9.298%   $59.9609   $59.96   $59.95   $60.00  
  Purchase #4 $226.93   3.834%   $235.6305   $235.63   $235.65   $235.60  
  Purchase #5 $226.92   13.344%   $257.2002   $257.20   $257.20   $257.20  
  Purchase #6 $75.69   4.514%   $79.1066   $79.11   $79.10   $79.10  
  Purchase #7 $162.32   11.712%   $181.3309   $181.33   $181.35   $181.30  
  7 purchase totals = $1,045.98       $1,134.6072   $1,134.61   $1,134.65   $1,134.50