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	$50.41	5.666%	$53.2662	$53.27	$53.25	$53.30
Purchase #2	$247.38	13.371%	$280.4572	$280.46	$280.45	$280.50
Purchase #3	$93.29	9.237%	$101.9072	$101.91	$101.90	$101.90
Purchase #4	$71.37	7.112%	$76.4458	$76.45	$76.45	$76.40
Purchase #5	$117.39	5.434%	$123.769	$123.77	$123.75	$123.80
Purchase #6	$125.41	11.662%	$140.0353	$140.04	$140.05	$140.00
Purchase #7	$51.38	3.369%	$53.111	$53.11	$53.10	$53.10
7 purchase totals =	$756.63		$828.9917	$829.01	$828.95	$829.00