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	$143.59	10.571%	$158.7689	$158.77	$158.75	$158.80
Purchase #2	$41.63	10.401%	$45.9599	$45.96	$45.95	$46.00
Purchase #3	$48.77	4.465%	$50.9476	$50.95	$50.95	$50.90
Purchase #4	$142.42	4.198%	$148.3988	$148.40	$148.40	$148.40
Purchase #5	$248.36	13.357%	$281.5334	$281.53	$281.55	$281.50
Purchase #6	$82.72	6.517%	$88.1109	$88.11	$88.10	$88.10
Purchase #7	$111.76	8.137%	$120.8539	$120.85	$120.85	$120.90
7 purchase totals =	$819.25		$894.5734	$894.57	$894.55	$894.60