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	$212.85	4.830%	$223.1307	$223.13	$223.15	$223.10
Purchase #2	$24.70	10.653%	$27.3313	$27.33	$27.35	$27.30
Purchase #3	$127.81	12.785%	$144.1505	$144.15	$144.15	$144.20
Purchase #4	$34.33	9.813%	$37.6988	$37.70	$37.70	$37.70
Purchase #5	$211.72	11.173%	$235.3755	$235.38	$235.40	$235.40
Purchase #6	$246.87	3.287%	$254.9846	$254.98	$255.00	$255.00
Purchase #7	$24.90	9.189%	$27.1881	$27.19	$27.20	$27.20
7 purchase totals =	$883.18		$949.8595	$949.86	$949.95	$949.90