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	$134.89	7.377%	$144.8408	$144.84	$144.85	$144.80
Purchase #2	$188.34	11.185%	$209.4058	$209.41	$209.40	$209.40
Purchase #3	$242.31	5.382%	$255.3511	$255.35	$255.35	$255.40
Purchase #4	$250.79	5.502%	$264.5885	$264.59	$264.60	$264.60
Purchase #5	$164.79	13.191%	$186.5274	$186.53	$186.55	$186.50
Purchase #6	$158.40	9.637%	$173.665	$173.67	$173.65	$173.70
Purchase #7	$32.55	7.685%	$35.0515	$35.05	$35.05	$35.10
7 purchase totals =	$1,172.07		$1,269.4301	$1,269.44	$1,269.45	$1,269.50