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	$64.54	8.371%	$69.9426	$69.94	$69.95	$69.90
Purchase #2	$234.97	11.440%	$261.8506	$261.85	$261.85	$261.90
Purchase #3	$81.74	7.421%	$87.8059	$87.81	$87.80	$87.80
Purchase #4	$173.75	4.664%	$181.8537	$181.85	$181.85	$181.90
Purchase #5	$236.98	8.276%	$256.5925	$256.59	$256.60	$256.60
Purchase #6	$98.73	5.334%	$103.9963	$104.00	$104.00	$104.00
Purchase #7	$94.44	5.665%	$99.79	$99.79	$99.80	$99.80
7 purchase totals =	$985.15		$1,061.8316	$1,061.83	$1,061.85	$1,061.90