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 $69.55   9.846%   $76.3979   $76.40   $76.40   $76.40  
  Purchase #2 $225.52   11.729%   $251.9712   $251.97   $251.95   $252.00  
  Purchase #3 $202.56   9.167%   $221.1287   $221.13   $221.15   $221.10  
  Purchase #4 $17.88   8.573%   $19.4129   $19.41   $19.40   $19.40  
  Purchase #5 $118.85   8.261%   $128.6682   $128.67   $128.65   $128.70  
  Purchase #6 $214.52   8.423%   $232.589   $232.59   $232.60   $232.60  
  Purchase #7 $218.68   11.671%   $244.2021   $244.20   $244.20   $244.20  
  7 purchase totals = $1,067.56       $1,174.3700   $1,174.37   $1,174.35   $1,174.40