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	$13.37	5.324%	$14.0818	$14.08	$14.10	$14.10
Purchase #2	$180.96	9.361%	$197.8997	$197.90	$197.90	$197.90
Purchase #3	$78.80	4.818%	$82.5966	$82.60	$82.60	$82.60
Purchase #4	$194.74	13.452%	$220.9364	$220.94	$220.95	$220.90
Purchase #5	$28.69	11.684%	$32.0421	$32.04	$32.05	$32.00
Purchase #6	$161.45	4.431%	$168.6038	$168.60	$168.60	$168.60
Purchase #7	$85.89	10.158%	$94.6147	$94.61	$94.60	$94.60
7 purchase totals =	$743.90		$810.7751	$810.77	$810.80	$810.70