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	$87.54	12.667%	$98.6287	$98.63	$98.65	$98.60
Purchase #2	$118.95	3.547%	$123.1692	$123.17	$123.15	$123.20
Purchase #3	$109.80	6.617%	$117.0655	$117.07	$117.05	$117.10
Purchase #4	$41.53	9.118%	$45.3167	$45.32	$45.30	$45.30
Purchase #5	$104.77	12.675%	$118.0496	$118.05	$118.05	$118.00
Purchase #6	$103.98	4.664%	$108.8296	$108.83	$108.85	$108.80
Purchase #7	$132.27	3.476%	$136.8677	$136.87	$136.85	$136.90
7 purchase totals =	$698.84		$747.9270	$747.94	$747.90	$747.90