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	$103.78	7.364%	$111.4224	$111.42	$111.40	$111.40
Purchase #2	$7.66	5.278%	$8.0643	$8.06	$8.05	$8.10
Purchase #3	$197.81	10.603%	$218.7838	$218.78	$218.80	$218.80
Purchase #4	$158.72	13.175%	$179.6314	$179.63	$179.65	$179.60
Purchase #5	$144.94	4.142%	$150.9434	$150.94	$150.95	$150.90
Purchase #6	$128.99	6.776%	$137.7304	$137.73	$137.75	$137.70
Purchase #7	$211.26	6.524%	$225.0426	$225.04	$225.05	$225.00
7 purchase totals =	$953.16		$1,031.6183	$1,031.60	$1,031.65	$1,031.50