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	$42.56	7.211%	$45.629	$45.63	$45.65	$45.60
Purchase #2	$150.85	13.754%	$171.5979	$171.60	$171.60	$171.60
Purchase #3	$172.94	3.361%	$178.7525	$178.75	$178.75	$178.80
Purchase #4	$213.42	6.170%	$226.588	$226.59	$226.60	$226.60
Purchase #5	$44.44	3.820%	$46.1376	$46.14	$46.15	$46.10
Purchase #6	$82.55	10.184%	$90.9569	$90.96	$90.95	$91.00
Purchase #7	$169.45	5.264%	$178.3698	$178.37	$178.35	$178.40
7 purchase totals =	$876.21		$938.0317	$938.04	$938.05	$938.10