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	$13.34	3.865%	$13.8556	$13.86	$13.85	$13.90
Purchase #2	$97.25	3.581%	$100.7325	$100.73	$100.75	$100.70
Purchase #3	$195.74	5.504%	$206.5135	$206.51	$206.50	$206.50
Purchase #4	$11.81	6.524%	$12.5805	$12.58	$12.60	$12.60
Purchase #5	$151.52	9.458%	$165.8508	$165.85	$165.85	$165.90
Purchase #6	$26.74	7.778%	$28.8198	$28.82	$28.80	$28.80
Purchase #7	$36.36	10.874%	$40.3138	$40.31	$40.30	$40.30
7 purchase totals =	$532.76		$568.6665	$568.66	$568.65	$568.70