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	$151.64	8.785%	$164.9616	$164.96	$164.95	$165.00
Purchase #2	$73.62	6.729%	$78.5739	$78.57	$78.55	$78.60
Purchase #3	$154.41	4.670%	$161.6209	$161.62	$161.60	$161.60
Purchase #4	$10.58	11.706%	$11.8185	$11.82	$11.80	$11.80
Purchase #5	$79.53	7.155%	$85.2204	$85.22	$85.20	$85.20
Purchase #6	$210.77	4.108%	$219.4284	$219.43	$219.45	$219.40
Purchase #7	$219.58	4.222%	$228.8507	$228.85	$228.85	$228.90
7 purchase totals =	$900.13		$950.4744	$950.47	$950.40	$950.50