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	$52.43	7.791%	$56.5148	$56.51	$56.50	$56.50
Purchase #2	$101.75	7.491%	$109.3721	$109.37	$109.35	$109.40
Purchase #3	$207.31	11.605%	$231.3683	$231.37	$231.35	$231.40
Purchase #4	$158.39	8.519%	$171.8832	$171.88	$171.90	$171.90
Purchase #5	$116.25	9.723%	$127.553	$127.55	$127.55	$127.60
Purchase #6	$188.46	8.475%	$204.432	$204.43	$204.45	$204.40
Purchase #7	$200.56	9.821%	$220.257	$220.26	$220.25	$220.30
7 purchase totals =	$1,025.15		$1,121.3804	$1,121.37	$1,121.35	$1,121.50