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	$132.33	10.784%	$146.6005	$146.60	$146.60	$146.60
Purchase #2	$35.35	3.276%	$36.5081	$36.51	$36.50	$36.50
Purchase #3	$114.87	6.609%	$122.4618	$122.46	$122.45	$122.50
Purchase #4	$104.67	11.173%	$116.3648	$116.36	$116.35	$116.40
Purchase #5	$128.60	11.539%	$143.4392	$143.44	$143.45	$143.40
Purchase #6	$216.45	3.443%	$223.9024	$223.90	$223.90	$223.90
Purchase #7	$85.88	7.285%	$92.1364	$92.14	$92.15	$92.10
7 purchase totals =	$818.15		$881.4132	$881.41	$881.40	$881.40