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	$144.47	10.860%	$160.1594	$160.16	$160.15	$160.20
Purchase #2	$147.66	11.356%	$164.4283	$164.43	$164.45	$164.40
Purchase #3	$185.58	3.196%	$191.5111	$191.51	$191.50	$191.50
Purchase #4	$18.90	4.287%	$19.7102	$19.71	$19.70	$19.70
Purchase #5	$217.38	10.422%	$240.0353	$240.04	$240.05	$240.00
Purchase #6	$222.93	13.831%	$253.7634	$253.76	$253.75	$253.80
Purchase #7	$51.44	9.570%	$56.3628	$56.36	$56.35	$56.40
7 purchase totals =	$988.36		$1,085.9705	$1,085.97	$1,085.95	$1,086.00