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	$131.33	11.380%	$146.2754	$146.28	$146.30	$146.30
Purchase #2	$166.53	11.611%	$185.8658	$185.87	$185.85	$185.90
Purchase #3	$42.88	3.762%	$44.4931	$44.49	$44.50	$44.50
Purchase #4	$105.26	4.870%	$110.3862	$110.39	$110.40	$110.40
Purchase #5	$91.70	3.619%	$95.0186	$95.02	$95.00	$95.00
Purchase #6	$130.74	13.784%	$148.7612	$148.76	$148.75	$148.80
Purchase #7	$230.58	3.453%	$238.5419	$238.54	$238.55	$238.50
7 purchase totals =	$899.02		$969.3422	$969.35	$969.35	$969.40