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	$228.98	13.680%	$260.3045	$260.30	$260.30	$260.30
Purchase #2	$240.95	6.417%	$256.4118	$256.41	$256.40	$256.40
Purchase #3	$203.38	7.541%	$218.7169	$218.72	$218.70	$218.70
Purchase #4	$147.63	7.289%	$158.3908	$158.39	$158.40	$158.40
Purchase #5	$59.90	9.192%	$65.406	$65.41	$65.40	$65.40
Purchase #6	$195.55	12.805%	$220.5902	$220.59	$220.60	$220.60
Purchase #7	$40.96	6.283%	$43.5335	$43.53	$43.55	$43.50
7 purchase totals =	$1,117.35		$1,223.3537	$1,223.35	$1,223.35	$1,223.30