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	$134.41	6.797%	$143.5458	$143.55	$143.55	$143.50
Purchase #2	$144.57	12.714%	$162.9506	$162.95	$162.95	$163.00
Purchase #3	$181.55	3.807%	$188.4616	$188.46	$188.45	$188.50
Purchase #4	$52.28	7.758%	$56.3359	$56.34	$56.35	$56.30
Purchase #5	$238.78	10.449%	$263.7301	$263.73	$263.75	$263.70
Purchase #6	$194.37	9.821%	$213.4591	$213.46	$213.45	$213.50
Purchase #7	$50.61	13.821%	$57.6048	$57.60	$57.60	$57.60
7 purchase totals =	$996.57		$1,086.0879	$1,086.09	$1,086.10	$1,086.10