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	$211.45	3.288%	$218.4025	$218.40	$218.40	$218.40
Purchase #2	$13.81	6.663%	$14.7302	$14.73	$14.75	$14.70
Purchase #3	$41.89	4.224%	$43.6594	$43.66	$43.65	$43.70
Purchase #4	$232.72	8.831%	$253.2715	$253.27	$253.25	$253.30
Purchase #5	$206.45	9.365%	$225.784	$225.78	$225.80	$225.80
Purchase #6	$159.66	6.744%	$170.4275	$170.43	$170.45	$170.40
Purchase #7	$38.25	11.315%	$42.578	$42.58	$42.60	$42.60
7 purchase totals =	$904.23		$968.8531	$968.85	$968.90	$968.90