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	$153.95	4.158%	$160.3512	$160.35	$160.35	$160.40
Purchase #2	$29.36	8.533%	$31.8653	$31.87	$31.85	$31.90
Purchase #3	$65.31	5.513%	$68.9105	$68.91	$68.90	$68.90
Purchase #4	$133.98	13.347%	$151.8623	$151.86	$151.85	$151.90
Purchase #5	$83.86	10.407%	$92.5873	$92.59	$92.60	$92.60
Purchase #6	$41.26	11.812%	$46.1336	$46.13	$46.15	$46.10
Purchase #7	$102.88	9.736%	$112.8964	$112.90	$112.90	$112.90
7 purchase totals =	$610.60		$664.6066	$664.61	$664.60	$664.70