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	$202.31	7.277%	$217.0321	$217.03	$217.05	$217.00
Purchase #2	$151.97	8.829%	$165.3874	$165.39	$165.40	$165.40
Purchase #3	$88.85	4.653%	$92.9842	$92.98	$93.00	$93.00
Purchase #4	$175.99	11.815%	$196.7832	$196.78	$196.80	$196.80
Purchase #5	$69.94	10.577%	$77.3376	$77.34	$77.35	$77.30
Purchase #6	$38.76	8.851%	$42.1906	$42.19	$42.20	$42.20
Purchase #7	$40.56	5.587%	$42.8261	$42.83	$42.85	$42.80
7 purchase totals =	$768.38		$834.5412	$834.54	$834.65	$834.50