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	$224.87	5.121%	$236.3856	$236.39	$236.40	$236.40
Purchase #2	$139.72	9.688%	$153.2561	$153.26	$153.25	$153.30
Purchase #3	$104.80	11.756%	$117.1203	$117.12	$117.10	$117.10
Purchase #4	$179.28	11.803%	$200.4404	$200.44	$200.45	$200.40
Purchase #5	$127.28	13.825%	$144.8765	$144.88	$144.90	$144.90
Purchase #6	$37.98	11.207%	$42.2364	$42.24	$42.25	$42.20
Purchase #7	$150.66	6.457%	$160.3881	$160.39	$160.40	$160.40
7 purchase totals =	$964.59		$1,054.7034	$1,054.72	$1,054.75	$1,054.70