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	$25.52	3.641%	$26.4492	$26.45	$26.45	$26.40
Purchase #2	$12.45	3.869%	$12.9317	$12.93	$12.95	$12.90
Purchase #3	$175.79	8.234%	$190.2645	$190.26	$190.25	$190.30
Purchase #4	$179.69	5.803%	$190.1174	$190.12	$190.10	$190.10
Purchase #5	$82.39	3.307%	$85.1146	$85.11	$85.10	$85.10
Purchase #6	$34.82	13.837%	$39.638	$39.64	$39.65	$39.60
Purchase #7	$122.76	3.752%	$127.366	$127.37	$127.35	$127.40
7 purchase totals =	$633.42		$671.8814	$671.88	$671.85	$671.80