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	$199.61	9.146%	$217.8663	$217.87	$217.85	$217.90
Purchase #2	$153.71	5.560%	$162.2563	$162.26	$162.25	$162.30
Purchase #3	$93.50	8.577%	$101.5195	$101.52	$101.50	$101.50
Purchase #4	$231.67	12.183%	$259.8944	$259.89	$259.90	$259.90
Purchase #5	$41.48	8.569%	$45.0344	$45.03	$45.05	$45.00
Purchase #6	$215.73	8.390%	$233.8297	$233.83	$233.85	$233.80
Purchase #7	$54.72	4.124%	$56.9767	$56.98	$57.00	$57.00
7 purchase totals =	$990.42		$1,077.3773	$1,077.38	$1,077.40	$1,077.40