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	$63.89	5.234%	$67.234	$67.23	$67.25	$67.20
Purchase #2	$126.43	4.763%	$132.4519	$132.45	$132.45	$132.50
Purchase #3	$140.68	7.474%	$151.1944	$151.19	$151.20	$151.20
Purchase #4	$205.37	7.710%	$221.204	$221.20	$221.20	$221.20
Purchase #5	$182.45	9.401%	$199.6021	$199.60	$199.60	$199.60
Purchase #6	$87.39	12.298%	$98.1372	$98.14	$98.15	$98.10
Purchase #7	$75.25	4.308%	$78.4918	$78.49	$78.50	$78.50
7 purchase totals =	$881.46		$948.3154	$948.30	$948.35	$948.30