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	$32.83	13.828%	$37.3697	$37.37	$37.35	$37.40
Purchase #2	$167.66	3.436%	$173.4208	$173.42	$173.40	$173.40
Purchase #3	$235.79	7.522%	$253.5261	$253.53	$253.55	$253.50
Purchase #4	$236.37	6.333%	$251.3393	$251.34	$251.35	$251.30
Purchase #5	$224.35	12.777%	$253.0152	$253.02	$253.00	$253.00
Purchase #6	$128.61	10.776%	$142.469	$142.47	$142.45	$142.50
Purchase #7	$126.27	12.440%	$141.978	$141.98	$142.00	$142.00
7 purchase totals =	$1,151.88		$1,253.1181	$1,253.13	$1,253.10	$1,253.10