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	$85.69	13.241%	$97.0362	$97.04	$97.05	$97.00
Purchase #2	$214.27	10.862%	$237.544	$237.54	$237.55	$237.50
Purchase #3	$103.76	12.597%	$116.8306	$116.83	$116.85	$116.80
Purchase #4	$158.46	4.687%	$165.887	$165.89	$165.90	$165.90
Purchase #5	$27.67	5.661%	$29.2364	$29.24	$29.25	$29.20
Purchase #6	$158.89	9.442%	$173.8924	$173.89	$173.90	$173.90
Purchase #7	$157.69	4.824%	$165.297	$165.30	$165.30	$165.30
7 purchase totals =	$906.43		$985.7236	$985.73	$985.80	$985.60