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	$30.48	9.606%	$33.4079	$33.41	$33.40	$33.40
Purchase #2	$234.56	8.857%	$255.335	$255.34	$255.35	$255.30
Purchase #3	$117.37	4.809%	$123.0143	$123.01	$123.00	$123.00
Purchase #4	$12.56	12.662%	$14.1503	$14.15	$14.15	$14.20
Purchase #5	$107.34	8.587%	$116.5573	$116.56	$116.55	$116.60
Purchase #6	$166.61	9.337%	$182.1664	$182.17	$182.15	$182.20
Purchase #7	$156.80	6.859%	$167.5549	$167.55	$167.55	$167.60
7 purchase totals =	$825.72		$892.1861	$892.19	$892.15	$892.30