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	$235.85	8.760%	$256.5105	$256.51	$256.50	$256.50
Purchase #2	$84.73	8.321%	$91.7804	$91.78	$91.80	$91.80
Purchase #3	$57.73	7.697%	$62.1735	$62.17	$62.15	$62.20
Purchase #4	$81.61	8.755%	$88.755	$88.76	$88.75	$88.80
Purchase #5	$238.74	7.142%	$255.7908	$255.79	$255.80	$255.80
Purchase #6	$61.48	8.390%	$66.6382	$66.64	$66.65	$66.60
Purchase #7	$143.75	11.361%	$160.0814	$160.08	$160.10	$160.10
7 purchase totals =	$903.89		$981.7298	$981.73	$981.75	$981.80