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	$250.77	5.222%	$263.8652	$263.87	$263.85	$263.90
Purchase #2	$177.36	12.568%	$199.6506	$199.65	$199.65	$199.70
Purchase #3	$72.79	6.262%	$77.3481	$77.35	$77.35	$77.30
Purchase #4	$196.74	9.717%	$215.8572	$215.86	$215.85	$215.90
Purchase #5	$105.39	13.264%	$119.3689	$119.37	$119.35	$119.40
Purchase #6	$55.44	5.532%	$58.5069	$58.51	$58.50	$58.50
Purchase #7	$76.93	6.426%	$81.8735	$81.87	$81.85	$81.90
7 purchase totals =	$935.42		$1,016.4704	$1,016.48	$1,016.40	$1,016.60