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	$66.38	9.443%	$72.6483	$72.65	$72.65	$72.60
Purchase #2	$40.40	9.249%	$44.1366	$44.14	$44.15	$44.10
Purchase #3	$248.50	6.140%	$263.7579	$263.76	$263.75	$263.80
Purchase #4	$73.78	5.249%	$77.6527	$77.65	$77.65	$77.70
Purchase #5	$197.78	12.487%	$222.4768	$222.48	$222.50	$222.50
Purchase #6	$110.90	8.821%	$120.6825	$120.68	$120.70	$120.70
Purchase #7	$47.32	11.139%	$52.591	$52.59	$52.60	$52.60
7 purchase totals =	$785.06		$853.9458	$853.95	$854.00	$854.00