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	$77.61	11.207%	$86.3078	$86.31	$86.30	$86.30
Purchase #2	$24.94	11.834%	$27.8914	$27.89	$27.90	$27.90
Purchase #3	$101.97	3.561%	$105.6012	$105.60	$105.60	$105.60
Purchase #4	$32.84	7.125%	$35.1799	$35.18	$35.20	$35.20
Purchase #5	$88.58	8.117%	$95.77	$95.77	$95.75	$95.80
Purchase #6	$148.83	4.225%	$155.1181	$155.12	$155.10	$155.10
Purchase #7	$155.89	10.130%	$171.6817	$171.68	$171.70	$171.70
7 purchase totals =	$630.66		$677.5501	$677.55	$677.55	$677.60