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	$91.71	8.554%	$99.5549	$99.55	$99.55	$99.60
Purchase #2	$95.38	10.423%	$105.3215	$105.32	$105.30	$105.30
Purchase #3	$12.89	8.822%	$14.0272	$14.03	$14.05	$14.00
Purchase #4	$55.89	6.745%	$59.6598	$59.66	$59.65	$59.70
Purchase #5	$34.47	13.165%	$39.008	$39.01	$39.00	$39.00
Purchase #6	$204.69	4.160%	$213.2051	$213.21	$213.20	$213.20
Purchase #7	$250.88	12.323%	$281.7959	$281.80	$281.80	$281.80
7 purchase totals =	$745.91		$812.5724	$812.58	$812.55	$812.60