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	$160.27	7.479%	$172.2566	$172.26	$172.25	$172.30
Purchase #2	$51.72	5.389%	$54.5072	$54.51	$54.50	$54.50
Purchase #3	$25.44	10.614%	$28.1402	$28.14	$28.15	$28.10
Purchase #4	$65.45	6.813%	$69.9091	$69.91	$69.90	$69.90
Purchase #5	$180.51	5.697%	$190.7937	$190.79	$190.80	$190.80
Purchase #6	$170.78	8.188%	$184.7635	$184.76	$184.75	$184.80
Purchase #7	$61.56	7.737%	$66.3229	$66.32	$66.30	$66.30
7 purchase totals =	$715.73		$766.6932	$766.69	$766.65	$766.70