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	$227.85	3.677%	$236.228	$236.23	$236.25	$236.20
Purchase #2	$54.73	11.366%	$60.9506	$60.95	$60.95	$61.00
Purchase #3	$81.36	11.480%	$90.7001	$90.70	$90.70	$90.70
Purchase #4	$225.81	13.152%	$255.5085	$255.51	$255.50	$255.50
Purchase #5	$57.95	6.821%	$61.9028	$61.90	$61.90	$61.90
Purchase #6	$198.49	6.236%	$210.8678	$210.87	$210.85	$210.90
Purchase #7	$118.40	7.632%	$127.4363	$127.44	$127.45	$127.40
7 purchase totals =	$964.59		$1,043.5941	$1,043.60	$1,043.60	$1,043.60