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	$232.48	12.485%	$261.5051	$261.51	$261.50	$261.50
Purchase #2	$206.61	5.606%	$218.1926	$218.19	$218.20	$218.20
Purchase #3	$224.50	3.867%	$233.1814	$233.18	$233.20	$233.20
Purchase #4	$152.81	3.751%	$158.5419	$158.54	$158.55	$158.50
Purchase #5	$17.52	7.534%	$18.84	$18.84	$18.85	$18.80
Purchase #6	$77.63	9.685%	$85.1485	$85.15	$85.15	$85.10
Purchase #7	$206.82	6.685%	$220.6459	$220.65	$220.65	$220.60
7 purchase totals =	$1,118.37		$1,196.0554	$1,196.06	$1,196.10	$1,195.90