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	$43.34	12.169%	$48.614	$48.61	$48.60	$48.60
Purchase #2	$34.63	8.358%	$37.5244	$37.52	$37.50	$37.50
Purchase #3	$63.27	6.474%	$67.3661	$67.37	$67.35	$67.40
Purchase #4	$54.34	5.777%	$57.4792	$57.48	$57.50	$57.50
Purchase #5	$77.52	7.761%	$83.5363	$83.54	$83.55	$83.50
Purchase #6	$97.43	10.221%	$107.3883	$107.39	$107.40	$107.40
Purchase #7	$74.85	6.711%	$79.8732	$79.87	$79.85	$79.90
7 purchase totals =	$445.38		$481.7815	$481.78	$481.75	$481.80