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	$198.45	10.330%	$218.9499	$218.95	$218.95	$218.90
Purchase #2	$176.54	7.398%	$189.6004	$189.60	$189.60	$189.60
Purchase #3	$80.94	7.338%	$86.8794	$86.88	$86.90	$86.90
Purchase #4	$173.51	4.849%	$181.9235	$181.92	$181.90	$181.90
Purchase #5	$78.69	5.654%	$83.1391	$83.14	$83.15	$83.10
Purchase #6	$55.34	8.210%	$59.8834	$59.88	$59.90	$59.90
Purchase #7	$140.80	3.166%	$145.2577	$145.26	$145.25	$145.30
7 purchase totals =	$904.27		$965.6334	$965.63	$965.65	$965.60