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	$231.71	13.777%	$263.6327	$263.63	$263.65	$263.60
Purchase #2	$144.69	4.221%	$150.7974	$150.80	$150.80	$150.80
Purchase #3	$100.61	9.279%	$109.9456	$109.95	$109.95	$109.90
Purchase #4	$65.68	12.433%	$73.846	$73.85	$73.85	$73.80
Purchase #5	$245.93	3.707%	$255.0466	$255.05	$255.05	$255.00
Purchase #6	$61.37	8.306%	$66.4674	$66.47	$66.45	$66.50
Purchase #7	$85.65	11.442%	$95.4501	$95.45	$95.45	$95.50
7 purchase totals =	$935.64		$1,015.1858	$1,015.20	$1,015.20	$1,015.10