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	$172.94	12.339%	$194.2791	$194.28	$194.30	$194.30
Purchase #2	$14.77	7.689%	$15.9057	$15.91	$15.90	$15.90
Purchase #3	$170.79	11.707%	$190.7844	$190.78	$190.80	$190.80
Purchase #4	$247.40	11.795%	$276.5808	$276.58	$276.60	$276.60
Purchase #5	$55.35	7.190%	$59.3297	$59.33	$59.35	$59.30
Purchase #6	$201.69	13.582%	$229.0835	$229.08	$229.10	$229.10
Purchase #7	$236.87	10.826%	$262.5135	$262.51	$262.50	$262.50
7 purchase totals =	$1,099.81		$1,228.4767	$1,228.47	$1,228.55	$1,228.50