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	$150.33	7.176%	$161.1177	$161.12	$161.10	$161.10
Purchase #2	$82.91	7.562%	$89.1797	$89.18	$89.20	$89.20
Purchase #3	$214.59	13.723%	$244.0382	$244.04	$244.05	$244.00
Purchase #4	$36.28	9.174%	$39.6083	$39.61	$39.60	$39.60
Purchase #5	$136.88	3.403%	$141.538	$141.54	$141.55	$141.50
Purchase #6	$192.74	11.295%	$214.51	$214.51	$214.50	$214.50
Purchase #7	$9.89	5.758%	$10.4595	$10.46	$10.45	$10.50
7 purchase totals =	$823.62		$900.4514	$900.46	$900.45	$900.40