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	$155.25	6.380%	$165.155	$165.16	$165.15	$165.20
Purchase #2	$220.43	10.767%	$244.1637	$244.16	$244.15	$244.20
Purchase #3	$234.31	13.778%	$266.5932	$266.59	$266.60	$266.60
Purchase #4	$99.69	4.725%	$104.4004	$104.40	$104.40	$104.40
Purchase #5	$40.70	5.424%	$42.9076	$42.91	$42.90	$42.90
Purchase #6	$48.74	3.658%	$50.5229	$50.52	$50.50	$50.50
Purchase #7	$162.25	6.441%	$172.7005	$172.70	$172.70	$172.70
7 purchase totals =	$961.37		$1,046.4433	$1,046.44	$1,046.40	$1,046.50