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	$168.60	11.132%	$187.3686	$187.37	$187.35	$187.40
Purchase #2	$181.59	7.822%	$195.794	$195.79	$195.80	$195.80
Purchase #3	$81.96	11.864%	$91.6837	$91.68	$91.70	$91.70
Purchase #4	$167.93	5.312%	$176.8504	$176.85	$176.85	$176.90
Purchase #5	$90.94	9.810%	$99.8612	$99.86	$99.85	$99.90
Purchase #6	$40.40	8.202%	$43.7136	$43.71	$43.70	$43.70
Purchase #7	$59.80	9.364%	$65.3997	$65.40	$65.40	$65.40
7 purchase totals =	$791.22		$860.6712	$860.66	$860.65	$860.80