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	$181.46	4.549%	$189.7146	$189.71	$189.70	$189.70
Purchase #2	$12.52	10.222%	$13.7998	$13.80	$13.80	$13.80
Purchase #3	$240.92	6.708%	$257.0809	$257.08	$257.10	$257.10
Purchase #4	$140.58	13.749%	$159.9083	$159.91	$159.90	$159.90
Purchase #5	$117.53	8.814%	$127.8891	$127.89	$127.90	$127.90
Purchase #6	$229.89	10.314%	$253.6009	$253.60	$253.60	$253.60
Purchase #7	$185.29	12.737%	$208.8904	$208.89	$208.90	$208.90
7 purchase totals =	$1,108.19		$1,210.8840	$1,210.88	$1,210.90	$1,210.90