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	$78.95	13.472%	$89.5861	$89.59	$89.60	$89.60
Purchase #2	$118.56	10.117%	$130.5547	$130.55	$130.55	$130.60
Purchase #3	$156.90	4.702%	$164.2774	$164.28	$164.30	$164.30
Purchase #4	$149.76	7.836%	$161.4952	$161.50	$161.50	$161.50
Purchase #5	$5.69	10.274%	$6.2746	$6.27	$6.25	$6.30
Purchase #6	$32.94	6.847%	$35.1954	$35.20	$35.20	$35.20
Purchase #7	$157.34	11.864%	$176.0068	$176.01	$176.00	$176.00
7 purchase totals =	$700.14		$763.3902	$763.40	$763.40	$763.50