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	$158.96	8.544%	$172.5415	$172.54	$172.55	$172.50
Purchase #2	$35.94	4.286%	$37.4804	$37.48	$37.50	$37.50
Purchase #3	$73.87	3.472%	$76.4348	$76.43	$76.45	$76.40
Purchase #4	$168.84	9.672%	$185.1702	$185.17	$185.15	$185.20
Purchase #5	$5.46	13.573%	$6.2011	$6.20	$6.20	$6.20
Purchase #6	$38.67	13.460%	$43.875	$43.88	$43.90	$43.90
Purchase #7	$50.69	6.143%	$53.8039	$53.80	$53.80	$53.80
7 purchase totals =	$532.43		$575.5069	$575.50	$575.55	$575.50