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	$94.75	6.697%	$101.0954	$101.10	$101.10	$101.10
Purchase #2	$99.38	11.338%	$110.6477	$110.65	$110.65	$110.60
Purchase #3	$94.71	5.482%	$99.902	$99.90	$99.90	$99.90
Purchase #4	$159.60	3.138%	$164.6082	$164.61	$164.60	$164.60
Purchase #5	$48.95	7.482%	$52.6124	$52.61	$52.60	$52.60
Purchase #6	$196.73	11.345%	$219.049	$219.05	$219.05	$219.00
Purchase #7	$60.77	10.131%	$66.9266	$66.93	$66.95	$66.90
7 purchase totals =	$754.89		$814.8413	$814.85	$814.85	$814.70