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	$160.27	9.706%	$175.8258	$175.83	$175.85	$175.80
Purchase #2	$32.56	5.352%	$34.3026	$34.30	$34.30	$34.30
Purchase #3	$157.27	13.248%	$178.1051	$178.11	$178.10	$178.10
Purchase #4	$139.88	12.788%	$157.7679	$157.77	$157.75	$157.80
Purchase #5	$99.71	12.459%	$112.1329	$112.13	$112.15	$112.10
Purchase #6	$176.35	13.726%	$200.5558	$200.56	$200.55	$200.60
Purchase #7	$30.60	9.232%	$33.425	$33.43	$33.45	$33.40
7 purchase totals =	$796.64		$892.1151	$892.13	$892.15	$892.10