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	$32.83	9.547%	$35.9643	$35.96	$35.95	$36.00
Purchase #2	$129.50	3.661%	$134.241	$134.24	$134.25	$134.20
Purchase #3	$78.98	4.741%	$82.7244	$82.72	$82.70	$82.70
Purchase #4	$183.87	6.426%	$195.6855	$195.69	$195.70	$195.70
Purchase #5	$220.93	9.517%	$241.9559	$241.96	$241.95	$242.00
Purchase #6	$73.50	12.183%	$82.4545	$82.45	$82.45	$82.50
Purchase #7	$95.28	9.756%	$104.5755	$104.58	$104.60	$104.60
7 purchase totals =	$814.89		$877.6011	$877.60	$877.60	$877.70