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	$103.61	8.116%	$112.019	$112.02	$112.00	$112.00
Purchase #2	$31.59	13.389%	$35.8196	$35.82	$35.80	$35.80
Purchase #3	$218.64	12.504%	$245.9787	$245.98	$246.00	$246.00
Purchase #4	$167.98	3.533%	$173.9147	$173.91	$173.90	$173.90
Purchase #5	$34.89	8.341%	$37.8002	$37.80	$37.80	$37.80
Purchase #6	$208.46	10.253%	$229.8334	$229.83	$229.85	$229.80
Purchase #7	$142.29	13.314%	$161.2345	$161.23	$161.25	$161.20
7 purchase totals =	$907.46		$996.6001	$996.59	$996.60	$996.50