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	$99.34	4.304%	$103.6156	$103.62	$103.60	$103.60
Purchase #2	$81.91	11.594%	$91.4066	$91.41	$91.40	$91.40
Purchase #3	$57.44	8.696%	$62.435	$62.44	$62.45	$62.40
Purchase #4	$81.54	12.341%	$91.6029	$91.60	$91.60	$91.60
Purchase #5	$141.97	3.180%	$146.4846	$146.48	$146.50	$146.50
Purchase #6	$200.46	8.819%	$218.1386	$218.14	$218.15	$218.10
Purchase #7	$25.48	7.331%	$27.3479	$27.35	$27.35	$27.30
7 purchase totals =	$688.14		$741.0312	$741.04	$741.05	$740.90