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	$133.51	3.483%	$138.1602	$138.16	$138.15	$138.20
Purchase #2	$105.36	5.644%	$111.3065	$111.31	$111.30	$111.30
Purchase #3	$147.68	6.576%	$157.3914	$157.39	$157.40	$157.40
Purchase #4	$99.84	11.202%	$111.0241	$111.02	$111.00	$111.00
Purchase #5	$88.77	4.565%	$92.8224	$92.82	$92.80	$92.80
Purchase #6	$246.48	3.859%	$255.9917	$255.99	$256.00	$256.00
Purchase #7	$96.60	10.648%	$106.886	$106.89	$106.90	$106.90
7 purchase totals =	$918.24		$973.5823	$973.58	$973.55	$973.60