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	$119.65	11.604%	$133.5342	$133.53	$133.55	$133.50
Purchase #2	$57.27	3.170%	$59.0855	$59.09	$59.10	$59.10
Purchase #3	$113.94	8.507%	$123.6329	$123.63	$123.65	$123.60
Purchase #4	$63.89	8.847%	$69.5423	$69.54	$69.55	$69.50
Purchase #5	$153.72	11.226%	$170.9766	$170.98	$171.00	$171.00
Purchase #6	$248.45	7.554%	$267.2179	$267.22	$267.20	$267.20
Purchase #7	$96.31	4.492%	$100.6362	$100.64	$100.65	$100.60
7 purchase totals =	$853.23		$924.6256	$924.63	$924.70	$924.50