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	$56.42	7.180%	$60.471	$60.47	$60.45	$60.50
Purchase #2	$190.95	12.194%	$214.2344	$214.23	$214.25	$214.20
Purchase #3	$92.83	6.569%	$98.928	$98.93	$98.95	$98.90
Purchase #4	$99.51	3.133%	$102.6276	$102.63	$102.65	$102.60
Purchase #5	$183.77	12.584%	$206.8956	$206.90	$206.90	$206.90
Purchase #6	$204.95	11.155%	$227.8122	$227.81	$227.80	$227.80
Purchase #7	$82.89	10.511%	$91.6026	$91.60	$91.60	$91.60
7 purchase totals =	$911.32		$1,002.5714	$1,002.57	$1,002.60	$1,002.50