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	$235.38	13.608%	$267.4105	$267.41	$267.40	$267.40
Purchase #2	$84.91	6.321%	$90.2772	$90.28	$90.30	$90.30
Purchase #3	$49.46	11.691%	$55.2424	$55.24	$55.25	$55.20
Purchase #4	$224.68	11.608%	$250.7609	$250.76	$250.75	$250.80
Purchase #5	$185.35	11.408%	$206.4947	$206.49	$206.50	$206.50
Purchase #6	$108.64	4.719%	$113.7667	$113.77	$113.75	$113.80
Purchase #7	$72.45	6.499%	$77.1585	$77.16	$77.15	$77.20
7 purchase totals =	$960.87		$1,061.1109	$1,061.11	$1,061.10	$1,061.20