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	$140.83	8.504%	$152.8062	$152.81	$152.80	$152.80
Purchase #2	$117.37	12.369%	$131.8875	$131.89	$131.90	$131.90
Purchase #3	$213.73	10.188%	$235.5048	$235.50	$235.50	$235.50
Purchase #4	$48.43	10.760%	$53.6411	$53.64	$53.65	$53.60
Purchase #5	$94.43	10.805%	$104.6332	$104.63	$104.65	$104.60
Purchase #6	$187.78	5.702%	$198.4872	$198.49	$198.50	$198.50
Purchase #7	$249.75	13.326%	$283.0317	$283.03	$283.05	$283.00
7 purchase totals =	$1,052.32		$1,159.9917	$1,159.99	$1,160.05	$1,159.90