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	$56.60	8.471%	$61.3946	$61.39	$61.40	$61.40
Purchase #2	$60.67	11.750%	$67.7987	$67.80	$67.80	$67.80
Purchase #3	$89.96	10.716%	$99.6001	$99.60	$99.60	$99.60
Purchase #4	$242.51	4.533%	$253.503	$253.50	$253.50	$253.50
Purchase #5	$227.32	10.130%	$250.3475	$250.35	$250.35	$250.30
Purchase #6	$79.55	8.153%	$86.0357	$86.04	$86.05	$86.00
Purchase #7	$87.55	10.243%	$96.5177	$96.52	$96.50	$96.50
7 purchase totals =	$844.16		$915.1973	$915.20	$915.20	$915.10