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	$171.89	10.848%	$190.5366	$190.54	$190.55	$190.50
Purchase #2	$218.27	5.448%	$230.1613	$230.16	$230.15	$230.20
Purchase #3	$163.47	5.502%	$172.4641	$172.46	$172.45	$172.50
Purchase #4	$76.62	8.628%	$83.2308	$83.23	$83.25	$83.20
Purchase #5	$80.36	12.238%	$90.1945	$90.19	$90.20	$90.20
Purchase #6	$180.58	3.135%	$186.2412	$186.24	$186.25	$186.20
Purchase #7	$121.40	3.870%	$126.0982	$126.10	$126.10	$126.10
7 purchase totals =	$1,012.59		$1,078.9267	$1,078.92	$1,078.95	$1,078.90