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	$238.61	6.287%	$253.6114	$253.61	$253.60	$253.60
Purchase #2	$55.92	5.774%	$59.1488	$59.15	$59.15	$59.10
Purchase #3	$137.98	6.506%	$146.957	$146.96	$146.95	$147.00
Purchase #4	$192.30	11.207%	$213.8511	$213.85	$213.85	$213.90
Purchase #5	$144.87	7.526%	$155.7729	$155.77	$155.75	$155.80
Purchase #6	$206.90	7.634%	$222.6947	$222.69	$222.70	$222.70
Purchase #7	$47.68	8.703%	$51.8296	$51.83	$51.85	$51.80
7 purchase totals =	$1,024.26		$1,103.8655	$1,103.86	$1,103.85	$1,103.90