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	$209.32	8.239%	$226.5659	$226.57	$226.55	$226.60
Purchase #2	$73.52	12.211%	$82.4975	$82.50	$82.50	$82.50
Purchase #3	$30.98	4.558%	$32.3921	$32.39	$32.40	$32.40
Purchase #4	$64.72	5.651%	$68.3773	$68.38	$68.40	$68.40
Purchase #5	$65.42	11.187%	$72.7385	$72.74	$72.75	$72.70
Purchase #6	$241.53	8.200%	$261.3355	$261.34	$261.35	$261.30
Purchase #7	$78.87	13.200%	$89.2808	$89.28	$89.30	$89.30
7 purchase totals =	$764.36		$833.1876	$833.20	$833.25	$833.20