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	$94.68	13.220%	$107.1967	$107.20	$107.20	$107.20
Purchase #2	$70.85	10.850%	$78.5372	$78.54	$78.55	$78.50
Purchase #3	$233.84	12.359%	$262.7403	$262.74	$262.75	$262.70
Purchase #4	$54.60	9.141%	$59.591	$59.59	$59.60	$59.60
Purchase #5	$85.44	10.510%	$94.4197	$94.42	$94.40	$94.40
Purchase #6	$78.58	10.241%	$86.6274	$86.63	$86.65	$86.60
Purchase #7	$33.69	10.654%	$37.2793	$37.28	$37.30	$37.30
7 purchase totals =	$651.68		$726.3916	$726.40	$726.45	$726.30