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	$166.77	11.263%	$185.5533	$185.55	$185.55	$185.60
Purchase #2	$123.26	5.132%	$129.5857	$129.59	$129.60	$129.60
Purchase #3	$139.52	13.297%	$158.072	$158.07	$158.05	$158.10
Purchase #4	$50.43	11.648%	$56.3041	$56.30	$56.30	$56.30
Purchase #5	$206.30	13.478%	$234.1051	$234.11	$234.10	$234.10
Purchase #6	$157.70	6.622%	$168.1429	$168.14	$168.15	$168.10
Purchase #7	$170.71	3.621%	$176.8914	$176.89	$176.90	$176.90
7 purchase totals =	$1,014.69		$1,108.6545	$1,108.65	$1,108.65	$1,108.70