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	$158.41	5.137%	$166.5475	$166.55	$166.55	$166.50
Purchase #2	$56.88	3.822%	$59.054	$59.05	$59.05	$59.10
Purchase #3	$122.84	4.718%	$128.6356	$128.64	$128.65	$128.60
Purchase #4	$230.78	8.708%	$250.8763	$250.88	$250.90	$250.90
Purchase #5	$23.63	7.129%	$25.3146	$25.31	$25.30	$25.30
Purchase #6	$111.96	5.470%	$118.0842	$118.08	$118.10	$118.10
Purchase #7	$195.79	9.104%	$213.6147	$213.61	$213.60	$213.60
7 purchase totals =	$900.29		$962.1269	$962.12	$962.15	$962.10