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	$213.54	13.667%	$242.7245	$242.72	$242.70	$242.70
Purchase #2	$151.35	10.266%	$166.8876	$166.89	$166.90	$166.90
Purchase #3	$162.94	7.651%	$175.4065	$175.41	$175.40	$175.40
Purchase #4	$161.58	10.345%	$178.2955	$178.30	$178.30	$178.30
Purchase #5	$132.87	4.698%	$139.1122	$139.11	$139.10	$139.10
Purchase #6	$91.48	5.502%	$96.5132	$96.51	$96.50	$96.50
Purchase #7	$147.35	3.351%	$152.2877	$152.29	$152.30	$152.30
7 purchase totals =	$1,061.11		$1,151.2272	$1,151.23	$1,151.20	$1,151.20