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	$226.69	7.373%	$243.4039	$243.40	$243.40	$243.40
Purchase #2	$18.45	8.451%	$20.0092	$20.01	$20.00	$20.00
Purchase #3	$69.71	5.304%	$73.4074	$73.41	$73.40	$73.40
Purchase #4	$231.32	5.553%	$244.1652	$244.17	$244.15	$244.20
Purchase #5	$82.36	10.370%	$90.9007	$90.90	$90.90	$90.90
Purchase #6	$151.53	8.792%	$164.8525	$164.85	$164.85	$164.90
Purchase #7	$21.68	13.311%	$24.5658	$24.57	$24.55	$24.60
7 purchase totals =	$801.74		$861.3047	$861.31	$861.25	$861.40