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	$142.60	12.638%	$160.6218	$160.62	$160.60	$160.60
Purchase #2	$59.51	11.167%	$66.1555	$66.16	$66.15	$66.20
Purchase #3	$31.83	11.754%	$35.5713	$35.57	$35.55	$35.60
Purchase #4	$115.52	3.246%	$119.2698	$119.27	$119.25	$119.30
Purchase #5	$154.30	11.440%	$171.9519	$171.95	$171.95	$172.00
Purchase #6	$209.56	7.425%	$225.1198	$225.12	$225.10	$225.10
Purchase #7	$228.56	13.504%	$259.4247	$259.42	$259.40	$259.40
7 purchase totals =	$941.88		$1,038.1148	$1,038.11	$1,038.00	$1,038.20