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	$53.28	12.511%	$59.9459	$59.95	$59.95	$59.90
Purchase #2	$23.76	4.353%	$24.7943	$24.79	$24.80	$24.80
Purchase #3	$185.75	3.660%	$192.5485	$192.55	$192.55	$192.50
Purchase #4	$222.56	5.480%	$234.7563	$234.76	$234.75	$234.80
Purchase #5	$25.45	12.175%	$28.5485	$28.55	$28.55	$28.50
Purchase #6	$153.29	12.740%	$172.8191	$172.82	$172.80	$172.80
Purchase #7	$246.45	9.697%	$270.3483	$270.35	$270.35	$270.30
7 purchase totals =	$910.54		$983.7609	$983.77	$983.75	$983.60