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	$79.63	7.410%	$85.5306	$85.53	$85.55	$85.50
Purchase #2	$235.46	6.424%	$250.586	$250.59	$250.60	$250.60
Purchase #3	$57.73	6.728%	$61.6141	$61.61	$61.60	$61.60
Purchase #4	$172.34	6.414%	$183.3939	$183.39	$183.40	$183.40
Purchase #5	$183.32	13.552%	$208.1635	$208.16	$208.15	$208.20
Purchase #6	$12.67	12.273%	$14.225	$14.23	$14.25	$14.20
Purchase #7	$217.40	5.860%	$230.1396	$230.14	$230.15	$230.10
7 purchase totals =	$958.55		$1,033.6527	$1,033.65	$1,033.70	$1,033.60