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	$51.36	13.654%	$58.3727	$58.37	$58.35	$58.40
Purchase #2	$206.34	5.862%	$218.4357	$218.44	$218.45	$218.40
Purchase #3	$77.36	6.709%	$82.5501	$82.55	$82.55	$82.60
Purchase #4	$206.60	4.300%	$215.4838	$215.48	$215.50	$215.50
Purchase #5	$59.36	4.780%	$62.1974	$62.20	$62.20	$62.20
Purchase #6	$206.66	12.233%	$231.9407	$231.94	$231.95	$231.90
Purchase #7	$54.36	8.779%	$59.1323	$59.13	$59.15	$59.10
7 purchase totals =	$862.04		$928.1127	$928.11	$928.15	$928.10