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	$163.66	11.506%	$182.4907	$182.49	$182.50	$182.50
Purchase #2	$76.27	13.604%	$86.6458	$86.65	$86.65	$86.60
Purchase #3	$137.81	9.187%	$150.4706	$150.47	$150.45	$150.50
Purchase #4	$74.25	5.740%	$78.512	$78.51	$78.50	$78.50
Purchase #5	$156.30	12.155%	$175.2983	$175.30	$175.30	$175.30
Purchase #6	$227.83	8.519%	$247.2388	$247.24	$247.25	$247.20
Purchase #7	$205.97	6.277%	$218.8987	$218.90	$218.90	$218.90
7 purchase totals =	$1,042.09		$1,139.5549	$1,139.56	$1,139.55	$1,139.50