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	$89.41	13.539%	$101.5152	$101.52	$101.50	$101.50
Purchase #2	$119.26	3.554%	$123.4985	$123.50	$123.50	$123.50
Purchase #3	$113.56	3.358%	$117.3733	$117.37	$117.35	$117.40
Purchase #4	$20.67	5.288%	$21.763	$21.76	$21.75	$21.80
Purchase #5	$81.37	5.357%	$85.729	$85.73	$85.75	$85.70
Purchase #6	$190.94	8.124%	$206.452	$206.45	$206.45	$206.50
Purchase #7	$148.65	4.527%	$155.3794	$155.38	$155.40	$155.40
7 purchase totals =	$763.86		$811.7104	$811.71	$811.70	$811.80