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	$56.68	13.484%	$64.3227	$64.32	$64.30	$64.30
Purchase #2	$165.34	13.870%	$188.2727	$188.27	$188.25	$188.30
Purchase #3	$37.59	5.163%	$39.5308	$39.53	$39.55	$39.50
Purchase #4	$79.86	12.438%	$89.793	$89.79	$89.80	$89.80
Purchase #5	$235.48	7.616%	$253.4142	$253.41	$253.40	$253.40
Purchase #6	$244.68	12.336%	$274.8637	$274.86	$274.85	$274.90
Purchase #7	$45.99	13.483%	$52.1908	$52.19	$52.20	$52.20
7 purchase totals =	$865.62		$962.3879	$962.37	$962.35	$962.40