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	$170.50	4.732%	$178.5681	$178.57	$178.55	$178.60
Purchase #2	$54.44	13.797%	$61.9511	$61.95	$61.95	$62.00
Purchase #3	$245.63	12.202%	$275.6018	$275.60	$275.60	$275.60
Purchase #4	$153.84	4.728%	$161.1136	$161.11	$161.10	$161.10
Purchase #5	$204.90	12.189%	$229.8753	$229.88	$229.90	$229.90
Purchase #6	$69.78	10.555%	$77.1453	$77.15	$77.15	$77.10
Purchase #7	$133.64	4.230%	$139.293	$139.29	$139.30	$139.30
7 purchase totals =	$1,032.73		$1,123.5482	$1,123.55	$1,123.55	$1,123.60