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	$63.28	9.690%	$69.4118	$69.41	$69.40	$69.40
Purchase #2	$211.47	6.614%	$225.4566	$225.46	$225.45	$225.50
Purchase #3	$235.34	3.289%	$243.0803	$243.08	$243.10	$243.10
Purchase #4	$127.53	8.697%	$138.6213	$138.62	$138.60	$138.60
Purchase #5	$100.59	6.284%	$106.9111	$106.91	$106.90	$106.90
Purchase #6	$241.60	10.330%	$266.5573	$266.56	$266.55	$266.60
Purchase #7	$55.83	7.256%	$59.881	$59.88	$59.90	$59.90
7 purchase totals =	$1,035.64		$1,109.9194	$1,109.92	$1,109.90	$1,110.00