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	$235.82	6.603%	$251.3912	$251.39	$251.40	$251.40
Purchase #2	$49.45	9.515%	$54.1552	$54.16	$54.15	$54.20
Purchase #3	$70.63	3.195%	$72.8866	$72.89	$72.90	$72.90
Purchase #4	$150.74	6.425%	$160.425	$160.43	$160.45	$160.40
Purchase #5	$157.73	3.308%	$162.9477	$162.95	$162.95	$162.90
Purchase #6	$46.85	8.490%	$50.8276	$50.83	$50.85	$50.80
Purchase #7	$202.76	3.814%	$210.4933	$210.49	$210.50	$210.50
7 purchase totals =	$913.98		$963.1266	$963.14	$963.20	$963.10