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	$217.34	7.749%	$234.1817	$234.18	$234.20	$234.20
Purchase #2	$191.45	3.339%	$197.8425	$197.84	$197.85	$197.80
Purchase #3	$108.65	13.650%	$123.4807	$123.48	$123.50	$123.50
Purchase #4	$123.81	5.405%	$130.5019	$130.50	$130.50	$130.50
Purchase #5	$127.69	13.421%	$144.8273	$144.83	$144.85	$144.80
Purchase #6	$95.28	10.276%	$105.071	$105.07	$105.05	$105.10
Purchase #7	$82.74	8.746%	$89.9764	$89.98	$90.00	$90.00
7 purchase totals =	$946.96		$1,025.8815	$1,025.88	$1,025.95	$1,025.90