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	$213.81	6.128%	$226.9123	$226.91	$226.90	$226.90
Purchase #2	$136.87	3.490%	$141.6468	$141.65	$141.65	$141.60
Purchase #3	$62.84	6.292%	$66.7939	$66.79	$66.80	$66.80
Purchase #4	$179.61	11.126%	$199.5934	$199.59	$199.60	$199.60
Purchase #5	$38.85	9.240%	$42.4397	$42.44	$42.45	$42.40
Purchase #6	$77.34	10.513%	$85.4708	$85.47	$85.45	$85.50
Purchase #7	$197.94	10.279%	$218.2863	$218.29	$218.30	$218.30
7 purchase totals =	$907.26		$981.1432	$981.14	$981.15	$981.10