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	$232.80	13.115%	$263.3317	$263.33	$263.35	$263.30
Purchase #2	$35.95	5.603%	$37.9643	$37.96	$37.95	$38.00
Purchase #3	$121.63	6.551%	$129.598	$129.60	$129.60	$129.60
Purchase #4	$47.65	11.569%	$53.1626	$53.16	$53.15	$53.20
Purchase #5	$70.66	10.513%	$78.0885	$78.09	$78.10	$78.10
Purchase #6	$38.48	10.736%	$42.6112	$42.61	$42.60	$42.60
Purchase #7	$106.30	11.383%	$118.4001	$118.40	$118.40	$118.40
7 purchase totals =	$653.47		$723.1564	$723.15	$723.15	$723.20