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	$39.49	11.140%	$43.8892	$43.89	$43.90	$43.90
Purchase #2	$15.31	10.627%	$16.937	$16.94	$16.95	$16.90
Purchase #3	$190.26	9.566%	$208.4603	$208.46	$208.45	$208.50
Purchase #4	$99.40	5.144%	$104.5131	$104.51	$104.50	$104.50
Purchase #5	$100.72	4.458%	$105.2101	$105.21	$105.20	$105.20
Purchase #6	$182.49	5.360%	$192.2715	$192.27	$192.25	$192.30
Purchase #7	$69.62	5.481%	$73.4359	$73.44	$73.45	$73.40
7 purchase totals =	$697.29		$744.7171	$744.72	$744.70	$744.70