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	$107.59	4.175%	$112.0819	$112.08	$112.10	$112.10
Purchase #2	$24.78	10.632%	$27.4146	$27.41	$27.40	$27.40
Purchase #3	$6.90	10.252%	$7.6074	$7.61	$7.60	$7.60
Purchase #4	$137.40	9.704%	$150.7333	$150.73	$150.75	$150.70
Purchase #5	$95.70	11.691%	$106.8883	$106.89	$106.90	$106.90
Purchase #6	$72.25	9.478%	$79.0979	$79.10	$79.10	$79.10
Purchase #7	$126.65	3.725%	$131.3677	$131.37	$131.35	$131.40
7 purchase totals =	$571.27		$615.1911	$615.19	$615.20	$615.20