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 $59.52   10.464%   $65.7482   $65.75   $65.75   $65.70  
  Purchase #2 $210.82   6.176%   $223.8402   $223.84   $223.85   $223.80  
  Purchase #3 $248.60   7.431%   $267.0735   $267.07   $267.05   $267.10  
  Purchase #4 $147.36   4.172%   $153.5079   $153.51   $153.50   $153.50  
  Purchase #5 $207.78   3.585%   $215.2289   $215.23   $215.25   $215.20  
  Purchase #6 $26.88   12.471%   $30.2322   $30.23   $30.25   $30.20  
  Purchase #7 $74.27   7.281%   $79.6776   $79.68   $79.70   $79.70  
  7 purchase totals = $975.23       $1,035.3085   $1,035.31   $1,035.35   $1,035.20