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	$194.95	12.720%	$219.7476	$219.75	$219.75	$219.70
Purchase #2	$47.29	6.700%	$50.4584	$50.46	$50.45	$50.50
Purchase #3	$84.54	5.692%	$89.352	$89.35	$89.35	$89.40
Purchase #4	$61.69	4.105%	$64.2224	$64.22	$64.20	$64.20
Purchase #5	$49.79	6.816%	$53.1837	$53.18	$53.20	$53.20
Purchase #6	$150.87	10.620%	$166.8924	$166.89	$166.90	$166.90
Purchase #7	$116.57	11.790%	$130.3136	$130.31	$130.30	$130.30
7 purchase totals =	$705.70		$774.1701	$774.16	$774.15	$774.20