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	$24.93	4.260%	$25.992	$25.99	$26.00	$26.00
Purchase #2	$186.82	5.224%	$196.5795	$196.58	$196.60	$196.60
Purchase #3	$174.28	13.834%	$198.3899	$198.39	$198.40	$198.40
Purchase #4	$78.49	12.362%	$88.1929	$88.19	$88.20	$88.20
Purchase #5	$184.85	6.455%	$196.7821	$196.78	$196.80	$196.80
Purchase #6	$176.40	3.505%	$182.5828	$182.58	$182.60	$182.60
Purchase #7	$48.91	3.784%	$50.7608	$50.76	$50.75	$50.80
7 purchase totals =	$874.68		$939.2800	$939.27	$939.35	$939.40