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	$141.52	5.195%	$148.872	$148.87	$148.85	$148.90
Purchase #2	$161.43	11.780%	$180.4465	$180.45	$180.45	$180.40
Purchase #3	$185.54	3.675%	$192.3586	$192.36	$192.35	$192.40
Purchase #4	$222.60	9.479%	$243.7003	$243.70	$243.70	$243.70
Purchase #5	$162.68	4.339%	$169.7387	$169.74	$169.75	$169.70
Purchase #6	$57.45	3.518%	$59.4711	$59.47	$59.45	$59.50
Purchase #7	$198.43	11.447%	$221.1443	$221.14	$221.15	$221.10
7 purchase totals =	$1,129.65		$1,215.7315	$1,215.73	$1,215.70	$1,215.70