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	$159.98	7.332%	$171.7097	$171.71	$171.70	$171.70
Purchase #2	$204.42	4.308%	$213.2264	$213.23	$213.25	$213.20
Purchase #3	$244.66	7.180%	$262.2266	$262.23	$262.25	$262.20
Purchase #4	$55.93	12.152%	$62.7266	$62.73	$62.75	$62.70
Purchase #5	$21.38	13.428%	$24.2509	$24.25	$24.25	$24.30
Purchase #6	$138.36	10.228%	$152.5115	$152.51	$152.50	$152.50
Purchase #7	$123.94	3.764%	$128.6051	$128.61	$128.60	$128.60
7 purchase totals =	$948.67		$1,015.2568	$1,015.27	$1,015.30	$1,015.20