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	$65.71	9.823%	$72.1647	$72.16	$72.15	$72.20
Purchase #2	$189.61	6.404%	$201.7526	$201.75	$201.75	$201.80
Purchase #3	$33.79	3.834%	$35.0855	$35.09	$35.10	$35.10
Purchase #4	$168.40	3.180%	$173.7551	$173.76	$173.75	$173.80
Purchase #5	$223.78	6.302%	$237.8826	$237.88	$237.90	$237.90
Purchase #6	$13.91	11.569%	$15.5192	$15.52	$15.50	$15.50
Purchase #7	$187.65	4.793%	$196.6441	$196.64	$196.65	$196.60
7 purchase totals =	$882.85		$932.8038	$932.80	$932.80	$932.90