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	$53.72	10.796%	$59.5196	$59.52	$59.50	$59.50
Purchase #2	$33.38	6.140%	$35.4295	$35.43	$35.45	$35.40
Purchase #3	$211.43	3.769%	$219.3988	$219.40	$219.40	$219.40
Purchase #4	$10.89	4.541%	$11.3845	$11.38	$11.40	$11.40
Purchase #5	$130.45	4.231%	$135.9693	$135.97	$135.95	$136.00
Purchase #6	$197.76	12.183%	$221.8531	$221.85	$221.85	$221.90
Purchase #7	$176.61	4.541%	$184.6299	$184.63	$184.65	$184.60
7 purchase totals =	$814.24		$868.1847	$868.18	$868.20	$868.20