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	$146.85	12.541%	$165.2665	$165.27	$165.25	$165.30
Purchase #2	$137.36	11.223%	$152.7759	$152.78	$152.80	$152.80
Purchase #3	$148.96	11.500%	$166.0904	$166.09	$166.10	$166.10
Purchase #4	$210.26	3.688%	$218.0144	$218.01	$218.00	$218.00
Purchase #5	$136.82	11.408%	$152.4284	$152.43	$152.45	$152.40
Purchase #6	$136.36	3.304%	$140.8653	$140.87	$140.85	$140.90
Purchase #7	$248.61	5.194%	$261.5228	$261.52	$261.50	$261.50
7 purchase totals =	$1,165.22		$1,256.9637	$1,256.97	$1,256.95	$1,257.00