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	$59.74	11.681%	$66.7182	$66.72	$66.70	$66.70
Purchase #2	$5.60	4.867%	$5.8726	$5.87	$5.85	$5.90
Purchase #3	$55.56	3.355%	$57.424	$57.42	$57.40	$57.40
Purchase #4	$87.74	13.820%	$99.8657	$99.87	$99.85	$99.90
Purchase #5	$155.42	8.411%	$168.4924	$168.49	$168.50	$168.50
Purchase #6	$108.93	11.310%	$121.25	$121.25	$121.25	$121.30
Purchase #7	$105.40	10.368%	$116.3279	$116.33	$116.35	$116.30
7 purchase totals =	$578.39		$635.9508	$635.95	$635.90	$636.00