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	$93.54	5.404%	$98.5949	$98.59	$98.60	$98.60
Purchase #2	$90.61	9.756%	$99.4499	$99.45	$99.45	$99.40
Purchase #3	$237.79	4.410%	$248.2765	$248.28	$248.30	$248.30
Purchase #4	$67.66	3.725%	$70.1803	$70.18	$70.20	$70.20
Purchase #5	$29.78	8.253%	$32.2377	$32.24	$32.25	$32.20
Purchase #6	$131.55	12.776%	$148.3568	$148.36	$148.35	$148.40
Purchase #7	$104.89	4.790%	$109.9142	$109.91	$109.90	$109.90
7 purchase totals =	$755.82		$807.0103	$807.01	$807.05	$807.00