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	$208.83	6.697%	$222.8153	$222.82	$222.80	$222.80
Purchase #2	$48.93	6.748%	$52.2318	$52.23	$52.25	$52.20
Purchase #3	$238.55	11.396%	$265.7352	$265.74	$265.75	$265.70
Purchase #4	$60.62	7.704%	$65.2902	$65.29	$65.30	$65.30
Purchase #5	$89.91	11.417%	$100.175	$100.18	$100.20	$100.20
Purchase #6	$158.69	13.622%	$180.3068	$180.31	$180.30	$180.30
Purchase #7	$77.45	5.738%	$81.8941	$81.89	$81.90	$81.90
7 purchase totals =	$882.98		$968.4484	$968.46	$968.50	$968.40