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	$43.90	11.289%	$48.8559	$48.86	$48.85	$48.90
Purchase #2	$132.71	7.337%	$142.4469	$142.45	$142.45	$142.40
Purchase #3	$182.28	3.654%	$188.9405	$188.94	$188.95	$188.90
Purchase #4	$120.57	8.534%	$130.8594	$130.86	$130.85	$130.90
Purchase #5	$201.42	11.179%	$223.9367	$223.94	$223.95	$223.90
Purchase #6	$187.52	9.867%	$206.0226	$206.02	$206.00	$206.00
Purchase #7	$33.37	12.153%	$37.4255	$37.43	$37.45	$37.40
7 purchase totals =	$901.77		$978.4875	$978.50	$978.50	$978.40