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 $179.35   8.746%   $195.036   $195.04   $195.05   $195.00  
  Purchase #2 $211.43   11.307%   $235.3364   $235.34   $235.35   $235.30  
  Purchase #3 $49.93   6.852%   $53.3512   $53.35   $53.35   $53.40  
  Purchase #4 $168.67   5.519%   $177.9789   $177.98   $178.00   $178.00  
  Purchase #5 $34.49   10.201%   $38.0083   $38.01   $38.00   $38.00  
  Purchase #6 $117.64   3.160%   $121.3574   $121.36   $121.35   $121.40  
  Purchase #7 $162.83   10.823%   $180.4531   $180.45   $180.45   $180.50  
  7 purchase totals = $924.34       $1,001.5213   $1,001.53   $1,001.55   $1,001.60