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	$62.54	7.873%	$67.4638	$67.46	$67.45	$67.50
Purchase #2	$117.43	10.806%	$130.1195	$130.12	$130.10	$130.10
Purchase #3	$123.39	5.863%	$130.6244	$130.62	$130.60	$130.60
Purchase #4	$159.76	3.801%	$165.8325	$165.83	$165.85	$165.80
Purchase #5	$5.54	11.583%	$6.1817	$6.18	$6.20	$6.20
Purchase #6	$244.37	8.598%	$265.3809	$265.38	$265.40	$265.40
Purchase #7	$247.53	8.650%	$268.9413	$268.94	$268.95	$268.90
7 purchase totals =	$960.56		$1,034.5441	$1,034.53	$1,034.55	$1,034.50