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	$38.60	4.316%	$40.266	$40.27	$40.25	$40.30
Purchase #2	$58.26	5.564%	$61.5016	$61.50	$61.50	$61.50
Purchase #3	$239.50	8.818%	$260.6191	$260.62	$260.60	$260.60
Purchase #4	$52.79	12.609%	$59.4463	$59.45	$59.45	$59.40
Purchase #5	$135.57	12.508%	$152.5271	$152.53	$152.55	$152.50
Purchase #6	$219.63	8.305%	$237.8703	$237.87	$237.85	$237.90
Purchase #7	$119.34	10.399%	$131.7502	$131.75	$131.75	$131.80
7 purchase totals =	$863.69		$943.9806	$943.99	$943.95	$944.00