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	$140.67	7.386%	$151.0599	$151.06	$151.05	$151.10
Purchase #2	$247.31	3.145%	$255.0879	$255.09	$255.10	$255.10
Purchase #3	$172.97	3.866%	$179.657	$179.66	$179.65	$179.70
Purchase #4	$24.97	3.781%	$25.9141	$25.91	$25.90	$25.90
Purchase #5	$149.31	7.480%	$160.4784	$160.48	$160.50	$160.50
Purchase #6	$104.47	5.135%	$109.8345	$109.83	$109.85	$109.80
Purchase #7	$37.94	5.186%	$39.9076	$39.91	$39.90	$39.90
7 purchase totals =	$877.64		$921.9394	$921.94	$921.95	$922.00