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	$32.93	8.117%	$35.6029	$35.60	$35.60	$35.60
Purchase #2	$156.73	7.523%	$168.5208	$168.52	$168.50	$168.50
Purchase #3	$213.45	6.500%	$227.3243	$227.32	$227.30	$227.30
Purchase #4	$72.40	5.276%	$76.2198	$76.22	$76.20	$76.20
Purchase #5	$134.83	4.699%	$141.1657	$141.17	$141.15	$141.20
Purchase #6	$153.76	11.801%	$171.9052	$171.91	$171.90	$171.90
Purchase #7	$190.93	6.814%	$203.94	$203.94	$203.95	$203.90
7 purchase totals =	$955.03		$1,024.6787	$1,024.68	$1,024.60	$1,024.60