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	$150.34	9.353%	$164.4013	$164.40	$164.40	$164.40
Purchase #2	$111.58	5.760%	$118.007	$118.01	$118.00	$118.00
Purchase #3	$112.30	10.310%	$123.8781	$123.88	$123.90	$123.90
Purchase #4	$205.61	8.796%	$223.6955	$223.70	$223.70	$223.70
Purchase #5	$57.71	11.434%	$64.3086	$64.31	$64.30	$64.30
Purchase #6	$159.76	3.724%	$165.7095	$165.71	$165.70	$165.70
Purchase #7	$29.51	9.316%	$32.2592	$32.26	$32.25	$32.30
7 purchase totals =	$826.81		$892.2592	$892.27	$892.25	$892.30