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	$191.33	5.853%	$202.5285	$202.53	$202.55	$202.50
Purchase #2	$241.95	13.250%	$274.0084	$274.01	$274.00	$274.00
Purchase #3	$19.40	4.658%	$20.3037	$20.30	$20.30	$20.30
Purchase #4	$147.93	7.502%	$159.0277	$159.03	$159.05	$159.00
Purchase #5	$73.42	12.503%	$82.5997	$82.60	$82.60	$82.60
Purchase #6	$69.66	6.707%	$74.3321	$74.33	$74.35	$74.30
Purchase #7	$227.31	12.404%	$255.5055	$255.51	$255.50	$255.50
7 purchase totals =	$971.00		$1,068.3056	$1,068.31	$1,068.35	$1,068.20