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	$63.85	13.271%	$72.3235	$72.32	$72.30	$72.30
Purchase #2	$182.57	12.644%	$205.6542	$205.65	$205.65	$205.70
Purchase #3	$132.47	9.874%	$145.5501	$145.55	$145.55	$145.60
Purchase #4	$178.81	11.280%	$198.9798	$198.98	$199.00	$199.00
Purchase #5	$45.50	4.298%	$47.4556	$47.46	$47.45	$47.50
Purchase #6	$53.43	10.632%	$59.1107	$59.11	$59.10	$59.10
Purchase #7	$218.81	7.258%	$234.6912	$234.69	$234.70	$234.70
7 purchase totals =	$875.44		$963.7651	$963.76	$963.75	$963.90