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	$133.81	6.754%	$142.8475	$142.85	$142.85	$142.80
Purchase #2	$39.85	13.467%	$45.2166	$45.22	$45.20	$45.20
Purchase #3	$67.39	10.275%	$74.3143	$74.31	$74.30	$74.30
Purchase #4	$64.92	12.370%	$72.9506	$72.95	$72.95	$73.00
Purchase #5	$42.31	10.454%	$46.7331	$46.73	$46.75	$46.70
Purchase #6	$248.98	5.326%	$262.2407	$262.24	$262.25	$262.20
Purchase #7	$229.34	4.855%	$240.4745	$240.47	$240.45	$240.50
7 purchase totals =	$826.60		$884.7773	$884.77	$884.75	$884.70