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	$141.89	11.406%	$158.074	$158.07	$158.05	$158.10
Purchase #2	$183.39	4.275%	$191.2299	$191.23	$191.25	$191.20
Purchase #3	$40.89	10.682%	$45.2579	$45.26	$45.25	$45.30
Purchase #4	$110.48	12.819%	$124.6424	$124.64	$124.65	$124.60
Purchase #5	$47.29	13.404%	$53.6288	$53.63	$53.65	$53.60
Purchase #6	$89.54	7.717%	$96.4498	$96.45	$96.45	$96.40
Purchase #7	$59.48	8.182%	$64.3467	$64.35	$64.35	$64.30
7 purchase totals =	$672.96		$733.6295	$733.63	$733.65	$733.50