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	$9.93	9.403%	$10.8637	$10.86	$10.85	$10.90
Purchase #2	$27.59	6.858%	$29.4821	$29.48	$29.50	$29.50
Purchase #3	$32.79	13.616%	$37.2547	$37.25	$37.25	$37.30
Purchase #4	$67.73	7.677%	$72.9296	$72.93	$72.95	$72.90
Purchase #5	$27.25	4.444%	$28.461	$28.46	$28.45	$28.50
Purchase #6	$76.42	7.314%	$82.0094	$82.01	$82.00	$82.00
Purchase #7	$91.73	11.452%	$102.2349	$102.23	$102.25	$102.20
7 purchase totals =	$333.44		$363.2354	$363.22	$363.25	$363.30