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	$201.58	5.605%	$212.8786	$212.88	$212.90	$212.90
Purchase #2	$56.96	4.839%	$59.7163	$59.72	$59.70	$59.70
Purchase #3	$31.63	12.504%	$35.585	$35.59	$35.60	$35.60
Purchase #4	$199.95	5.638%	$211.2232	$211.22	$211.20	$211.20
Purchase #5	$37.66	11.854%	$42.1242	$42.12	$42.10	$42.10
Purchase #6	$24.57	11.467%	$27.3874	$27.39	$27.40	$27.40
Purchase #7	$217.84	7.167%	$233.4526	$233.45	$233.45	$233.50
7 purchase totals =	$770.19		$822.3673	$822.37	$822.35	$822.40