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	$63.38	3.740%	$65.7504	$65.75	$65.75	$65.80
Purchase #2	$72.82	11.387%	$81.112	$81.11	$81.10	$81.10
Purchase #3	$145.64	13.749%	$165.664	$165.66	$165.65	$165.70
Purchase #4	$99.64	12.235%	$111.831	$111.83	$111.85	$111.80
Purchase #5	$240.58	5.757%	$254.4302	$254.43	$254.45	$254.40
Purchase #6	$65.29	8.518%	$70.8514	$70.85	$70.85	$70.90
Purchase #7	$39.73	9.136%	$43.3597	$43.36	$43.35	$43.40
7 purchase totals =	$727.08		$792.9987	$792.99	$793.00	$793.10