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	$65.56	9.839%	$72.0104	$72.01	$72.00	$72.00
Purchase #2	$41.44	10.138%	$45.6412	$45.64	$45.65	$45.60
Purchase #3	$123.58	7.739%	$133.1439	$133.14	$133.15	$133.10
Purchase #4	$96.25	10.758%	$106.6046	$106.60	$106.60	$106.60
Purchase #5	$230.88	13.867%	$262.8961	$262.90	$262.90	$262.90
Purchase #6	$34.66	3.555%	$35.8922	$35.89	$35.90	$35.90
Purchase #7	$93.84	12.709%	$105.7661	$105.77	$105.75	$105.80
7 purchase totals =	$686.21		$761.9545	$761.95	$761.95	$761.90