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	$195.52	7.174%	$209.5466	$209.55	$209.55	$209.50
Purchase #2	$40.75	4.166%	$42.4476	$42.45	$42.45	$42.40
Purchase #3	$176.55	13.731%	$200.7921	$200.79	$200.80	$200.80
Purchase #4	$36.66	4.813%	$38.4244	$38.42	$38.40	$38.40
Purchase #5	$247.41	13.353%	$280.4467	$280.45	$280.45	$280.40
Purchase #6	$138.59	11.788%	$154.927	$154.93	$154.95	$154.90
Purchase #7	$226.90	10.542%	$250.8198	$250.82	$250.80	$250.80
7 purchase totals =	$1,062.38		$1,177.4042	$1,177.41	$1,177.40	$1,177.20