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	$113.70	8.750%	$123.6488	$123.65	$123.65	$123.60
Purchase #2	$53.65	5.325%	$56.5069	$56.51	$56.50	$56.50
Purchase #3	$154.43	11.167%	$171.6752	$171.68	$171.70	$171.70
Purchase #4	$205.44	3.541%	$212.7146	$212.71	$212.70	$212.70
Purchase #5	$202.80	12.372%	$227.8904	$227.89	$227.90	$227.90
Purchase #6	$48.84	7.559%	$52.5318	$52.53	$52.55	$52.50
Purchase #7	$166.78	4.569%	$174.4002	$174.40	$174.40	$174.40
7 purchase totals =	$945.64		$1,019.3679	$1,019.37	$1,019.40	$1,019.30