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	$127.25	3.714%	$131.9761	$131.98	$132.00	$132.00
Purchase #2	$226.66	7.860%	$244.4755	$244.48	$244.50	$244.50
Purchase #3	$201.86	7.228%	$216.4504	$216.45	$216.45	$216.50
Purchase #4	$26.98	5.149%	$28.3692	$28.37	$28.35	$28.40
Purchase #5	$185.61	9.770%	$203.7441	$203.74	$203.75	$203.70
Purchase #6	$40.42	5.452%	$42.6237	$42.62	$42.60	$42.60
Purchase #7	$147.54	10.133%	$162.4902	$162.49	$162.50	$162.50
7 purchase totals =	$956.32		$1,030.1292	$1,030.13	$1,030.15	$1,030.20