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	$125.58	4.475%	$131.1997	$131.20	$131.20	$131.20
Purchase #2	$105.71	5.522%	$111.5473	$111.55	$111.55	$111.50
Purchase #3	$230.31	7.200%	$246.8923	$246.89	$246.90	$246.90
Purchase #4	$86.59	10.139%	$95.3694	$95.37	$95.35	$95.40
Purchase #5	$144.50	11.454%	$161.051	$161.05	$161.05	$161.10
Purchase #6	$196.50	11.165%	$218.4392	$218.44	$218.45	$218.40
Purchase #7	$188.83	6.694%	$201.4703	$201.47	$201.45	$201.50
7 purchase totals =	$1,078.02		$1,165.9692	$1,165.97	$1,165.95	$1,166.00