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	$194.73	10.805%	$215.7706	$215.77	$215.75	$215.80
Purchase #2	$80.68	13.312%	$91.4201	$91.42	$91.40	$91.40
Purchase #3	$28.85	13.655%	$32.7895	$32.79	$32.80	$32.80
Purchase #4	$24.56	13.705%	$27.9259	$27.93	$27.95	$27.90
Purchase #5	$113.75	13.483%	$129.0869	$129.09	$129.10	$129.10
Purchase #6	$52.82	12.593%	$59.4716	$59.47	$59.45	$59.50
Purchase #7	$118.47	7.321%	$127.1432	$127.14	$127.15	$127.10
7 purchase totals =	$613.86		$683.6078	$683.61	$683.60	$683.60