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	$225.46	7.770%	$242.9782	$242.98	$243.00	$243.00
Purchase #2	$231.86	11.658%	$258.8902	$258.89	$258.90	$258.90
Purchase #3	$92.97	7.130%	$99.5988	$99.60	$99.60	$99.60
Purchase #4	$143.86	11.693%	$160.6815	$160.68	$160.70	$160.70
Purchase #5	$148.25	11.486%	$165.278	$165.28	$165.30	$165.30
Purchase #6	$157.59	9.485%	$172.5374	$172.54	$172.55	$172.50
Purchase #7	$49.39	7.828%	$53.2562	$53.26	$53.25	$53.30
7 purchase totals =	$1,049.38		$1,153.2203	$1,153.23	$1,153.30	$1,153.30