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	$43.29	13.849%	$49.2852	$49.29	$49.30	$49.30
Purchase #2	$213.78	3.699%	$221.6877	$221.69	$221.70	$221.70
Purchase #3	$209.39	6.222%	$222.4182	$222.42	$222.40	$222.40
Purchase #4	$135.62	4.266%	$141.4055	$141.41	$141.40	$141.40
Purchase #5	$90.89	4.868%	$95.3145	$95.31	$95.30	$95.30
Purchase #6	$185.27	12.584%	$208.5844	$208.58	$208.60	$208.60
Purchase #7	$245.89	8.122%	$265.8612	$265.86	$265.85	$265.90
7 purchase totals =	$1,124.13		$1,204.5567	$1,204.56	$1,204.55	$1,204.60