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	$51.78	12.516%	$58.2608	$58.26	$58.25	$58.30
Purchase #2	$96.65	7.499%	$103.8978	$103.90	$103.90	$103.90
Purchase #3	$48.51	11.783%	$54.2259	$54.23	$54.25	$54.20
Purchase #4	$54.56	13.665%	$62.0156	$62.02	$62.00	$62.00
Purchase #5	$66.69	3.479%	$69.0101	$69.01	$69.00	$69.00
Purchase #6	$82.80	5.526%	$87.3755	$87.38	$87.40	$87.40
Purchase #7	$87.58	3.197%	$90.3799	$90.38	$90.40	$90.40
7 purchase totals =	$488.57		$525.1656	$525.18	$525.20	$525.20