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	$210.43	12.362%	$236.4434	$236.44	$236.45	$236.40
Purchase #2	$145.64	3.341%	$150.5058	$150.51	$150.50	$150.50
Purchase #3	$71.84	8.741%	$78.1195	$78.12	$78.10	$78.10
Purchase #4	$175.97	5.427%	$185.5199	$185.52	$185.50	$185.50
Purchase #5	$82.77	4.279%	$86.3117	$86.31	$86.30	$86.30
Purchase #6	$89.39	5.377%	$94.1965	$94.20	$94.20	$94.20
Purchase #7	$60.34	8.702%	$65.5908	$65.59	$65.60	$65.60
7 purchase totals =	$836.38		$896.6876	$896.69	$896.65	$896.60