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	$91.63	7.259%	$98.2814	$98.28	$98.30	$98.30
Purchase #2	$34.73	9.269%	$37.9491	$37.95	$37.95	$37.90
Purchase #3	$180.37	5.588%	$190.4491	$190.45	$190.45	$190.40
Purchase #4	$215.60	13.199%	$244.057	$244.06	$244.05	$244.10
Purchase #5	$128.49	7.677%	$138.3542	$138.35	$138.35	$138.40
Purchase #6	$88.92	13.440%	$100.8708	$100.87	$100.85	$100.90
Purchase #7	$36.40	8.548%	$39.5115	$39.51	$39.50	$39.50
7 purchase totals =	$776.14		$849.4731	$849.47	$849.45	$849.50