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	$98.48	5.748%	$104.1406	$104.14	$104.15	$104.10
Purchase #2	$84.32	6.568%	$89.8581	$89.86	$89.85	$89.90
Purchase #3	$139.59	13.694%	$158.7055	$158.71	$158.70	$158.70
Purchase #4	$17.89	8.659%	$19.4391	$19.44	$19.45	$19.40
Purchase #5	$94.53	13.364%	$107.163	$107.16	$107.15	$107.20
Purchase #6	$105.66	10.697%	$116.9625	$116.96	$116.95	$117.00
Purchase #7	$13.26	4.641%	$13.8754	$13.88	$13.90	$13.90
7 purchase totals =	$553.73		$610.1442	$610.15	$610.15	$610.20