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	$224.96	11.504%	$250.8394	$250.84	$250.85	$250.80
Purchase #2	$242.76	9.686%	$266.2737	$266.27	$266.25	$266.30
Purchase #3	$205.39	11.435%	$228.8763	$228.88	$228.90	$228.90
Purchase #4	$214.51	3.186%	$221.3443	$221.34	$221.35	$221.30
Purchase #5	$102.37	13.805%	$116.5022	$116.50	$116.50	$116.50
Purchase #6	$99.28	13.284%	$112.4684	$112.47	$112.45	$112.50
Purchase #7	$42.31	7.216%	$45.3631	$45.36	$45.35	$45.40
7 purchase totals =	$1,131.58		$1,241.6674	$1,241.66	$1,241.65	$1,241.70