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	$213.93	3.118%	$220.6003	$220.60	$220.60	$220.60
Purchase #2	$6.81	8.565%	$7.3933	$7.39	$7.40	$7.40
Purchase #3	$77.65	10.136%	$85.5206	$85.52	$85.50	$85.50
Purchase #4	$55.73	12.233%	$62.5475	$62.55	$62.55	$62.50
Purchase #5	$67.91	12.667%	$76.5122	$76.51	$76.50	$76.50
Purchase #6	$159.95	7.659%	$172.2006	$172.20	$172.20	$172.20
Purchase #7	$55.61	11.207%	$61.8422	$61.84	$61.85	$61.80
7 purchase totals =	$637.59		$686.6167	$686.61	$686.60	$686.50