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	$30.34	5.695%	$32.0679	$32.07	$32.05	$32.10
Purchase #2	$150.72	10.216%	$166.1176	$166.12	$166.10	$166.10
Purchase #3	$54.52	8.599%	$59.2082	$59.21	$59.20	$59.20
Purchase #4	$146.52	13.567%	$166.3984	$166.40	$166.40	$166.40
Purchase #5	$42.38	13.438%	$48.075	$48.08	$48.10	$48.10
Purchase #6	$107.26	3.592%	$111.1128	$111.11	$111.10	$111.10
Purchase #7	$127.76	6.576%	$136.1615	$136.16	$136.15	$136.20
7 purchase totals =	$659.50		$719.1414	$719.15	$719.10	$719.20