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	$138.35	4.467%	$144.5301	$144.53	$144.55	$144.50
Purchase #2	$39.47	7.621%	$42.478	$42.48	$42.50	$42.50
Purchase #3	$52.55	13.821%	$59.8129	$59.81	$59.80	$59.80
Purchase #4	$15.26	4.551%	$15.9545	$15.95	$15.95	$16.00
Purchase #5	$175.41	3.828%	$182.1247	$182.12	$182.10	$182.10
Purchase #6	$80.28	7.264%	$86.1115	$86.11	$86.10	$86.10
Purchase #7	$152.84	13.773%	$173.8907	$173.89	$173.90	$173.90
7 purchase totals =	$654.16		$704.9024	$704.89	$704.90	$704.90