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	$229.87	13.719%	$261.4059	$261.41	$261.40	$261.40
Purchase #2	$53.49	11.154%	$59.4563	$59.46	$59.45	$59.50
Purchase #3	$217.57	12.588%	$244.9577	$244.96	$244.95	$245.00
Purchase #4	$31.26	12.244%	$35.0875	$35.09	$35.10	$35.10
Purchase #5	$146.92	12.181%	$164.8163	$164.82	$164.80	$164.80
Purchase #6	$153.27	3.763%	$159.0376	$159.04	$159.05	$159.00
Purchase #7	$89.43	13.127%	$101.1695	$101.17	$101.15	$101.20
7 purchase totals =	$921.81		$1,025.9308	$1,025.95	$1,025.90	$1,026.00