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	$178.43	10.230%	$196.6834	$196.68	$196.70	$196.70
Purchase #2	$144.73	11.731%	$161.7083	$161.71	$161.70	$161.70
Purchase #3	$121.64	3.728%	$126.1747	$126.17	$126.15	$126.20
Purchase #4	$114.55	7.634%	$123.2947	$123.29	$123.30	$123.30
Purchase #5	$65.88	3.809%	$68.3894	$68.39	$68.40	$68.40
Purchase #6	$99.73	11.480%	$111.179	$111.18	$111.20	$111.20
Purchase #7	$138.52	9.764%	$152.0451	$152.05	$152.05	$152.00
7 purchase totals =	$863.48		$939.4746	$939.47	$939.50	$939.50