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	$236.46	10.570%	$261.4538	$261.45	$261.45	$261.50
Purchase #2	$200.37	7.442%	$215.2815	$215.28	$215.30	$215.30
Purchase #3	$36.36	10.326%	$40.1145	$40.11	$40.10	$40.10
Purchase #4	$102.30	5.807%	$108.2406	$108.24	$108.25	$108.20
Purchase #5	$180.71	5.642%	$190.9057	$190.91	$190.90	$190.90
Purchase #6	$17.45	5.161%	$18.3506	$18.35	$18.35	$18.40
Purchase #7	$103.55	12.864%	$116.8707	$116.87	$116.85	$116.90
7 purchase totals =	$877.20		$951.2174	$951.21	$951.20	$951.30