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	$71.53	13.546%	$81.2195	$81.22	$81.20	$81.20
Purchase #2	$24.81	4.362%	$25.8922	$25.89	$25.90	$25.90
Purchase #3	$233.86	3.857%	$242.88	$242.88	$242.90	$242.90
Purchase #4	$218.31	4.805%	$228.7998	$228.80	$228.80	$228.80
Purchase #5	$80.86	3.632%	$83.7968	$83.80	$83.80	$83.80
Purchase #6	$72.52	12.316%	$81.4516	$81.45	$81.45	$81.50
Purchase #7	$169.31	9.188%	$184.8662	$184.87	$184.85	$184.90
7 purchase totals =	$871.20		$928.9061	$928.91	$928.90	$929.00