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	$211.53	5.503%	$223.1705	$223.17	$223.15	$223.20
Purchase #2	$198.37	3.195%	$204.7079	$204.71	$204.70	$204.70
Purchase #3	$135.45	5.213%	$142.511	$142.51	$142.50	$142.50
Purchase #4	$160.65	4.457%	$167.8102	$167.81	$167.80	$167.80
Purchase #5	$28.27	10.516%	$31.2429	$31.24	$31.25	$31.20
Purchase #6	$156.66	10.760%	$173.5166	$173.52	$173.50	$173.50
Purchase #7	$29.52	10.584%	$32.6444	$32.64	$32.65	$32.60
7 purchase totals =	$920.45		$975.6035	$975.60	$975.55	$975.50