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	$30.82	11.596%	$34.3939	$34.39	$34.40	$34.40
Purchase #2	$240.88	3.609%	$249.5734	$249.57	$249.55	$249.60
Purchase #3	$231.89	13.562%	$263.3389	$263.34	$263.35	$263.30
Purchase #4	$244.58	13.510%	$277.6228	$277.62	$277.60	$277.60
Purchase #5	$109.86	5.629%	$116.044	$116.04	$116.05	$116.00
Purchase #6	$94.58	11.698%	$105.644	$105.64	$105.65	$105.60
Purchase #7	$101.63	3.143%	$104.8242	$104.82	$104.80	$104.80
7 purchase totals =	$1,054.24		$1,151.4412	$1,151.42	$1,151.40	$1,151.30