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	$153.71	8.346%	$166.5386	$166.54	$166.55	$166.50
Purchase #2	$96.42	9.404%	$105.4873	$105.49	$105.50	$105.50
Purchase #3	$132.53	10.355%	$146.2535	$146.25	$146.25	$146.30
Purchase #4	$176.37	3.577%	$182.6788	$182.68	$182.70	$182.70
Purchase #5	$162.91	6.524%	$173.5382	$173.54	$173.55	$173.50
Purchase #6	$33.33	6.325%	$35.4381	$35.44	$35.45	$35.40
Purchase #7	$119.62	3.531%	$123.8438	$123.84	$123.85	$123.80
7 purchase totals =	$874.89		$933.7783	$933.78	$933.85	$933.70