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	$124.81	8.858%	$135.8657	$135.87	$135.85	$135.90
Purchase #2	$127.38	13.455%	$144.519	$144.52	$144.50	$144.50
Purchase #3	$161.89	12.718%	$182.4792	$182.48	$182.50	$182.50
Purchase #4	$90.84	10.782%	$100.6344	$100.63	$100.65	$100.60
Purchase #5	$35.57	8.858%	$38.7208	$38.72	$38.70	$38.70
Purchase #6	$115.92	3.107%	$119.5216	$119.52	$119.50	$119.50
Purchase #7	$188.35	3.455%	$194.8575	$194.86	$194.85	$194.90
7 purchase totals =	$844.76		$916.5982	$916.60	$916.55	$916.60