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	$36.41	3.518%	$37.6909	$37.69	$37.70	$37.70
Purchase #2	$71.97	9.804%	$79.0259	$79.03	$79.05	$79.00
Purchase #3	$53.58	7.363%	$57.5251	$57.53	$57.55	$57.50
Purchase #4	$57.71	6.709%	$61.5818	$61.58	$61.60	$61.60
Purchase #5	$137.42	4.414%	$143.4857	$143.49	$143.50	$143.50
Purchase #6	$60.29	10.157%	$66.4137	$66.41	$66.40	$66.40
Purchase #7	$35.37	3.228%	$36.5117	$36.51	$36.50	$36.50
7 purchase totals =	$452.75		$482.2348	$482.24	$482.30	$482.20