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	$131.77	7.653%	$141.8544	$141.85	$141.85	$141.90
Purchase #2	$250.38	10.590%	$276.8952	$276.90	$276.90	$276.90
Purchase #3	$134.81	8.744%	$146.5978	$146.60	$146.60	$146.60
Purchase #4	$109.97	7.706%	$118.4443	$118.44	$118.45	$118.40
Purchase #5	$189.83	5.766%	$200.7756	$200.78	$200.80	$200.80
Purchase #6	$50.27	13.606%	$57.1097	$57.11	$57.10	$57.10
Purchase #7	$232.25	4.581%	$242.8894	$242.89	$242.90	$242.90
7 purchase totals =	$1,099.28		$1,184.5664	$1,184.57	$1,184.60	$1,184.60