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	$206.58	5.654%	$218.26	$218.26	$218.25	$218.30
Purchase #2	$221.73	12.130%	$248.6258	$248.63	$248.65	$248.60
Purchase #3	$17.38	12.698%	$19.5869	$19.59	$19.60	$19.60
Purchase #4	$93.84	6.671%	$100.1001	$100.10	$100.10	$100.10
Purchase #5	$125.71	11.806%	$140.5513	$140.55	$140.55	$140.60
Purchase #6	$36.88	10.262%	$40.6646	$40.66	$40.65	$40.70
Purchase #7	$235.25	5.704%	$248.6687	$248.67	$248.65	$248.70
7 purchase totals =	$937.37		$1,016.4574	$1,016.46	$1,016.45	$1,016.60