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	$130.32	13.693%	$148.1647	$148.16	$148.15	$148.20
Purchase #2	$54.27	3.790%	$56.3268	$56.33	$56.35	$56.30
Purchase #3	$151.94	13.363%	$172.2437	$172.24	$172.25	$172.20
Purchase #4	$235.50	3.458%	$243.6436	$243.64	$243.65	$243.60
Purchase #5	$151.36	6.802%	$161.6555	$161.66	$161.65	$161.70
Purchase #6	$139.48	12.825%	$157.3683	$157.37	$157.35	$157.40
Purchase #7	$142.72	13.627%	$162.1685	$162.17	$162.15	$162.20
7 purchase totals =	$1,005.59		$1,101.5711	$1,101.57	$1,101.55	$1,101.60