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	$164.58	6.129%	$174.6671	$174.67	$174.65	$174.70
Purchase #2	$233.50	8.258%	$252.7824	$252.78	$252.80	$252.80
Purchase #3	$30.73	4.355%	$32.0683	$32.07	$32.05	$32.10
Purchase #4	$65.34	9.342%	$71.4441	$71.44	$71.45	$71.40
Purchase #5	$83.31	7.545%	$89.5957	$89.60	$89.60	$89.60
Purchase #6	$247.43	12.329%	$277.9356	$277.94	$277.95	$277.90
Purchase #7	$110.59	12.434%	$124.3408	$124.34	$124.35	$124.30
7 purchase totals =	$935.48		$1,022.8340	$1,022.84	$1,022.85	$1,022.80