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	$140.86	4.231%	$146.8198	$146.82	$146.80	$146.80
Purchase #2	$100.32	11.372%	$111.7284	$111.73	$111.75	$111.70
Purchase #3	$142.55	3.699%	$147.8229	$147.82	$147.80	$147.80
Purchase #4	$74.71	3.238%	$77.1291	$77.13	$77.15	$77.10
Purchase #5	$206.31	5.578%	$217.818	$217.82	$217.80	$217.80
Purchase #6	$214.64	8.276%	$232.4036	$232.40	$232.40	$232.40
Purchase #7	$133.99	5.674%	$141.5926	$141.59	$141.60	$141.60
7 purchase totals =	$1,013.38		$1,075.3144	$1,075.31	$1,075.30	$1,075.20