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	$143.49	13.790%	$163.2773	$163.28	$163.30	$163.30
Purchase #2	$157.58	4.403%	$164.5182	$164.52	$164.50	$164.50
Purchase #3	$244.72	9.621%	$268.2645	$268.26	$268.25	$268.30
Purchase #4	$114.67	7.605%	$123.3907	$123.39	$123.40	$123.40
Purchase #5	$142.76	7.111%	$152.9117	$152.91	$152.90	$152.90
Purchase #6	$119.56	12.334%	$134.3065	$134.31	$134.30	$134.30
Purchase #7	$43.42	7.376%	$46.6227	$46.62	$46.60	$46.60
7 purchase totals =	$966.20		$1,053.2916	$1,053.29	$1,053.25	$1,053.30