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	$147.51	5.423%	$155.5095	$155.51	$155.50	$155.50
Purchase #2	$30.89	11.812%	$34.5387	$34.54	$34.55	$34.50
Purchase #3	$72.90	6.783%	$77.8448	$77.84	$77.85	$77.80
Purchase #4	$213.84	6.555%	$227.8572	$227.86	$227.85	$227.90
Purchase #5	$223.43	13.847%	$254.3684	$254.37	$254.35	$254.40
Purchase #6	$140.58	11.640%	$156.9435	$156.94	$156.95	$156.90
Purchase #7	$165.36	4.485%	$172.7764	$172.78	$172.80	$172.80
7 purchase totals =	$994.51		$1,079.8385	$1,079.84	$1,079.85	$1,079.80