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	$9.65	7.865%	$10.409	$10.41	$10.40	$10.40
Purchase #2	$62.81	13.757%	$71.4508	$71.45	$71.45	$71.50
Purchase #3	$158.72	5.210%	$166.9893	$166.99	$167.00	$167.00
Purchase #4	$150.54	4.276%	$156.9771	$156.98	$157.00	$157.00
Purchase #5	$92.72	6.788%	$99.0138	$99.01	$99.00	$99.00
Purchase #6	$33.71	11.282%	$37.5132	$37.51	$37.50	$37.50
Purchase #7	$33.68	6.793%	$35.9679	$35.97	$35.95	$36.00
7 purchase totals =	$541.83		$578.3211	$578.32	$578.30	$578.40