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	$220.92	3.871%	$229.4718	$229.47	$229.45	$229.50
Purchase #2	$6.81	8.274%	$7.3735	$7.37	$7.35	$7.40
Purchase #3	$40.38	4.336%	$42.1309	$42.13	$42.15	$42.10
Purchase #4	$135.89	7.498%	$146.079	$146.08	$146.10	$146.10
Purchase #5	$65.56	5.705%	$69.3002	$69.30	$69.30	$69.30
Purchase #6	$190.92	8.242%	$206.6556	$206.66	$206.65	$206.70
Purchase #7	$241.78	5.683%	$255.5204	$255.52	$255.50	$255.50
7 purchase totals =	$902.26		$956.5314	$956.53	$956.50	$956.60