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	$203.34	6.237%	$216.0223	$216.02	$216.00	$216.00
Purchase #2	$219.29	11.640%	$244.8154	$244.82	$244.80	$244.80
Purchase #3	$16.73	8.476%	$18.148	$18.15	$18.15	$18.10
Purchase #4	$5.94	11.312%	$6.6119	$6.61	$6.60	$6.60
Purchase #5	$82.59	9.751%	$90.6434	$90.64	$90.65	$90.60
Purchase #6	$126.49	3.443%	$130.8451	$130.85	$130.85	$130.80
Purchase #7	$231.45	5.465%	$244.0987	$244.10	$244.10	$244.10
7 purchase totals =	$885.83		$951.1848	$951.19	$951.15	$951.00