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	$248.94	11.555%	$277.705	$277.71	$277.70	$277.70
Purchase #2	$167.92	10.658%	$185.8169	$185.82	$185.80	$185.80
Purchase #3	$174.67	13.155%	$197.6478	$197.65	$197.65	$197.60
Purchase #4	$137.96	6.855%	$147.4172	$147.42	$147.40	$147.40
Purchase #5	$184.74	8.423%	$200.3007	$200.30	$200.30	$200.30
Purchase #6	$172.39	7.610%	$185.5089	$185.51	$185.50	$185.50
Purchase #7	$241.81	3.605%	$250.5273	$250.53	$250.55	$250.50
7 purchase totals =	$1,328.43		$1,444.9238	$1,444.94	$1,444.90	$1,444.80