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	$106.56	3.758%	$110.5645	$110.56	$110.55	$110.60
Purchase #2	$215.62	4.752%	$225.8663	$225.87	$225.85	$225.90
Purchase #3	$135.32	11.562%	$150.9657	$150.97	$150.95	$151.00
Purchase #4	$30.42	5.460%	$32.0809	$32.08	$32.10	$32.10
Purchase #5	$119.34	3.430%	$123.4334	$123.43	$123.45	$123.40
Purchase #6	$61.28	10.337%	$67.6145	$67.61	$67.60	$67.60
Purchase #7	$199.73	9.255%	$218.215	$218.22	$218.20	$218.20
7 purchase totals =	$868.27		$928.7403	$928.74	$928.70	$928.80