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	$96.37	7.171%	$103.2807	$103.28	$103.30	$103.30
Purchase #2	$100.26	3.810%	$104.0799	$104.08	$104.10	$104.10
Purchase #3	$249.89	7.205%	$267.8946	$267.89	$267.90	$267.90
Purchase #4	$35.37	9.472%	$38.7202	$38.72	$38.70	$38.70
Purchase #5	$153.89	10.258%	$169.676	$169.68	$169.70	$169.70
Purchase #6	$56.66	4.377%	$59.14	$59.14	$59.15	$59.10
Purchase #7	$6.91	11.326%	$7.6926	$7.69	$7.70	$7.70
7 purchase totals =	$699.35		$750.4840	$750.48	$750.55	$750.50