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	$154.56	6.608%	$164.7733	$164.77	$164.75	$164.80
Purchase #2	$44.86	11.794%	$50.1508	$50.15	$50.15	$50.20
Purchase #3	$243.67	7.668%	$262.3546	$262.35	$262.35	$262.40
Purchase #4	$146.75	10.758%	$162.5374	$162.54	$162.55	$162.50
Purchase #5	$149.81	3.437%	$154.959	$154.96	$154.95	$155.00
Purchase #6	$220.89	13.815%	$251.406	$251.41	$251.40	$251.40
Purchase #7	$37.42	4.365%	$39.0534	$39.05	$39.05	$39.10
7 purchase totals =	$997.96		$1,085.2345	$1,085.23	$1,085.20	$1,085.40