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	$46.71	11.212%	$51.9471	$51.95	$51.95	$51.90
Purchase #2	$151.58	12.468%	$170.479	$170.48	$170.50	$170.50
Purchase #3	$185.80	5.722%	$196.4315	$196.43	$196.45	$196.40
Purchase #4	$19.25	5.759%	$20.3586	$20.36	$20.35	$20.40
Purchase #5	$93.84	6.842%	$100.2605	$100.26	$100.25	$100.30
Purchase #6	$110.62	12.408%	$124.3457	$124.35	$124.35	$124.30
Purchase #7	$166.35	12.175%	$186.6031	$186.60	$186.60	$186.60
7 purchase totals =	$774.15		$850.4255	$850.43	$850.45	$850.40