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	$207.53	11.220%	$230.8149	$230.81	$230.80	$230.80
Purchase #2	$231.45	8.292%	$250.6418	$250.64	$250.65	$250.60
Purchase #3	$35.75	5.768%	$37.8121	$37.81	$37.80	$37.80
Purchase #4	$62.58	7.760%	$67.4362	$67.44	$67.45	$67.40
Purchase #5	$176.83	7.544%	$190.1701	$190.17	$190.15	$190.20
Purchase #6	$144.64	4.628%	$151.3339	$151.33	$151.35	$151.30
Purchase #7	$129.89	13.540%	$147.4771	$147.48	$147.50	$147.50
7 purchase totals =	$988.67		$1,075.6861	$1,075.68	$1,075.70	$1,075.60