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	$190.60	13.472%	$216.2776	$216.28	$216.30	$216.30
Purchase #2	$28.41	4.787%	$29.77	$29.77	$29.75	$29.80
Purchase #3	$222.54	11.118%	$247.282	$247.28	$247.30	$247.30
Purchase #4	$55.96	7.483%	$60.1475	$60.15	$60.15	$60.10
Purchase #5	$136.94	8.704%	$148.8593	$148.86	$148.85	$148.90
Purchase #6	$89.45	11.495%	$99.7323	$99.73	$99.75	$99.70
Purchase #7	$239.84	4.419%	$250.4385	$250.44	$250.45	$250.40
7 purchase totals =	$963.74		$1,052.5072	$1,052.51	$1,052.55	$1,052.50