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	$42.25	3.132%	$43.5733	$43.57	$43.55	$43.60
Purchase #2	$127.90	11.116%	$142.1174	$142.12	$142.10	$142.10
Purchase #3	$148.53	8.610%	$161.3184	$161.32	$161.30	$161.30
Purchase #4	$237.52	6.292%	$252.4648	$252.46	$252.45	$252.50
Purchase #5	$83.91	8.865%	$91.3486	$91.35	$91.35	$91.30
Purchase #6	$97.90	12.595%	$110.2305	$110.23	$110.25	$110.20
Purchase #7	$178.38	7.342%	$191.4767	$191.48	$191.50	$191.50
7 purchase totals =	$916.39		$992.5297	$992.53	$992.50	$992.50