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	$178.85	7.335%	$191.9686	$191.97	$191.95	$192.00
Purchase #2	$35.39	11.588%	$39.491	$39.49	$39.50	$39.50
Purchase #3	$161.76	6.661%	$172.5348	$172.53	$172.55	$172.50
Purchase #4	$186.65	12.500%	$209.9813	$209.98	$210.00	$210.00
Purchase #5	$66.52	10.548%	$73.5365	$73.54	$73.55	$73.50
Purchase #6	$17.26	12.701%	$19.4522	$19.45	$19.45	$19.50
Purchase #7	$199.90	10.791%	$221.4712	$221.47	$221.45	$221.50
7 purchase totals =	$846.33		$928.4356	$928.43	$928.45	$928.50