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	$82.55	3.804%	$85.6902	$85.69	$85.70	$85.70
Purchase #2	$159.49	7.816%	$171.9557	$171.96	$171.95	$172.00
Purchase #3	$184.32	4.187%	$192.0375	$192.04	$192.05	$192.00
Purchase #4	$50.81	7.429%	$54.5847	$54.58	$54.60	$54.60
Purchase #5	$38.80	9.815%	$42.6082	$42.61	$42.60	$42.60
Purchase #6	$18.89	9.485%	$20.6817	$20.68	$20.70	$20.70
Purchase #7	$135.49	4.432%	$141.4949	$141.49	$141.50	$141.50
7 purchase totals =	$670.35		$709.0529	$709.05	$709.10	$709.10