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	$103.32	7.590%	$111.162	$111.16	$111.15	$111.20
Purchase #2	$71.38	6.577%	$76.0747	$76.07	$76.05	$76.10
Purchase #3	$74.80	11.557%	$83.4446	$83.44	$83.45	$83.40
Purchase #4	$117.49	11.148%	$130.5878	$130.59	$130.60	$130.60
Purchase #5	$212.42	8.703%	$230.9069	$230.91	$230.90	$230.90
Purchase #6	$69.57	13.164%	$78.7282	$78.73	$78.75	$78.70
Purchase #7	$123.72	4.216%	$128.936	$128.94	$128.95	$128.90
7 purchase totals =	$772.70		$839.8402	$839.84	$839.85	$839.80