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	$134.25	13.819%	$152.802	$152.80	$152.80	$152.80
Purchase #2	$55.64	5.162%	$58.5121	$58.51	$58.50	$58.50
Purchase #3	$238.84	12.749%	$269.2897	$269.29	$269.30	$269.30
Purchase #4	$243.90	9.520%	$267.1193	$267.12	$267.10	$267.10
Purchase #5	$51.31	13.672%	$58.3251	$58.33	$58.35	$58.30
Purchase #6	$33.63	7.765%	$36.2414	$36.24	$36.25	$36.20
Purchase #7	$114.37	11.266%	$127.2549	$127.25	$127.25	$127.30
7 purchase totals =	$871.94		$969.5445	$969.54	$969.55	$969.50