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	$124.31	4.759%	$130.2259	$130.23	$130.25	$130.20
Purchase #2	$49.82	9.326%	$54.4662	$54.47	$54.45	$54.50
Purchase #3	$243.73	8.438%	$264.2959	$264.30	$264.30	$264.30
Purchase #4	$248.63	3.212%	$256.616	$256.62	$256.60	$256.60
Purchase #5	$101.68	9.658%	$111.5003	$111.50	$111.50	$111.50
Purchase #6	$33.93	8.456%	$36.7991	$36.80	$36.80	$36.80
Purchase #7	$240.36	8.516%	$260.8291	$260.83	$260.85	$260.80
7 purchase totals =	$1,042.46		$1,114.7325	$1,114.75	$1,114.75	$1,114.70