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	$137.90	10.704%	$152.6608	$152.66	$152.65	$152.70
Purchase #2	$168.59	4.872%	$176.8037	$176.80	$176.80	$176.80
Purchase #3	$165.43	10.216%	$182.3303	$182.33	$182.35	$182.30
Purchase #4	$92.72	7.189%	$99.3856	$99.39	$99.40	$99.40
Purchase #5	$207.78	13.652%	$236.1461	$236.15	$236.15	$236.10
Purchase #6	$150.72	9.653%	$165.269	$165.27	$165.25	$165.30
Purchase #7	$64.50	13.198%	$73.0127	$73.01	$73.00	$73.00
7 purchase totals =	$987.64		$1,085.6082	$1,085.61	$1,085.60	$1,085.60