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	$113.58	7.517%	$122.1178	$122.12	$122.10	$122.10
Purchase #2	$185.65	5.719%	$196.2673	$196.27	$196.25	$196.30
Purchase #3	$36.46	8.693%	$39.6295	$39.63	$39.65	$39.60
Purchase #4	$129.43	5.771%	$136.8994	$136.90	$136.90	$136.90
Purchase #5	$38.54	11.193%	$42.8538	$42.85	$42.85	$42.90
Purchase #6	$227.93	8.713%	$247.7895	$247.79	$247.80	$247.80
Purchase #7	$68.70	6.110%	$72.8976	$72.90	$72.90	$72.90
7 purchase totals =	$800.29		$858.4549	$858.46	$858.45	$858.50