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	$180.91	8.563%	$196.4013	$196.40	$196.40	$196.40
Purchase #2	$245.74	11.599%	$274.2434	$274.24	$274.25	$274.20
Purchase #3	$48.46	4.635%	$50.7061	$50.71	$50.70	$50.70
Purchase #4	$209.44	10.521%	$231.4752	$231.48	$231.50	$231.50
Purchase #5	$155.40	7.655%	$167.2959	$167.30	$167.30	$167.30
Purchase #6	$166.58	11.126%	$185.1137	$185.11	$185.10	$185.10
Purchase #7	$128.77	8.162%	$139.2802	$139.28	$139.30	$139.30
7 purchase totals =	$1,135.30		$1,244.5158	$1,244.52	$1,244.55	$1,244.50