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	$119.55	6.421%	$127.2263	$127.23	$127.25	$127.20
Purchase #2	$224.52	12.142%	$251.7812	$251.78	$251.80	$251.80
Purchase #3	$31.62	4.700%	$33.1061	$33.11	$33.10	$33.10
Purchase #4	$242.80	11.341%	$270.3359	$270.34	$270.35	$270.30
Purchase #5	$183.85	7.258%	$197.1938	$197.19	$197.20	$197.20
Purchase #6	$98.87	12.814%	$111.5392	$111.54	$111.55	$111.50
Purchase #7	$155.30	6.511%	$165.4116	$165.41	$165.40	$165.40
7 purchase totals =	$1,056.51		$1,156.5941	$1,156.60	$1,156.65	$1,156.50