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	$42.57	10.615%	$47.0888	$47.09	$47.10	$47.10
Purchase #2	$10.49	9.313%	$11.4669	$11.47	$11.45	$11.50
Purchase #3	$63.86	12.346%	$71.7442	$71.74	$71.75	$71.70
Purchase #4	$118.31	4.712%	$123.8848	$123.88	$123.90	$123.90
Purchase #5	$113.60	10.365%	$125.3746	$125.37	$125.35	$125.40
Purchase #6	$23.48	7.773%	$25.3051	$25.31	$25.30	$25.30
Purchase #7	$35.58	8.680%	$38.6683	$38.67	$38.65	$38.70
7 purchase totals =	$407.89		$443.5327	$443.53	$443.50	$443.60