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	$200.89	7.306%	$215.567	$215.57	$215.55	$215.60
Purchase #2	$55.48	6.351%	$59.0035	$59.00	$59.00	$59.00
Purchase #3	$16.71	11.417%	$18.6178	$18.62	$18.60	$18.60
Purchase #4	$36.98	6.733%	$39.4699	$39.47	$39.45	$39.50
Purchase #5	$60.86	5.721%	$64.3418	$64.34	$64.35	$64.30
Purchase #6	$89.62	8.774%	$97.4833	$97.48	$97.50	$97.50
Purchase #7	$115.62	10.595%	$127.8699	$127.87	$127.85	$127.90
7 purchase totals =	$576.16		$622.3532	$622.35	$622.30	$622.40