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	$174.64	5.458%	$184.1719	$184.17	$184.15	$184.20
Purchase #2	$219.58	6.719%	$234.3336	$234.33	$234.35	$234.30
Purchase #3	$72.47	11.623%	$80.8932	$80.89	$80.90	$80.90
Purchase #4	$222.95	11.703%	$249.0418	$249.04	$249.05	$249.00
Purchase #5	$90.81	9.314%	$99.268	$99.27	$99.25	$99.30
Purchase #6	$47.70	12.394%	$53.6119	$53.61	$53.60	$53.60
Purchase #7	$47.37	13.268%	$53.6551	$53.66	$53.65	$53.70
7 purchase totals =	$875.52		$954.9755	$954.97	$954.95	$955.00