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	$124.86	9.850%	$137.1587	$137.16	$137.15	$137.20
Purchase #2	$158.29	13.322%	$179.3774	$179.38	$179.40	$179.40
Purchase #3	$83.61	3.379%	$86.4352	$86.44	$86.45	$86.40
Purchase #4	$249.70	12.259%	$280.3107	$280.31	$280.30	$280.30
Purchase #5	$155.93	12.498%	$175.4181	$175.42	$175.40	$175.40
Purchase #6	$60.45	11.552%	$67.4332	$67.43	$67.45	$67.40
Purchase #7	$5.87	11.152%	$6.5246	$6.52	$6.50	$6.50
7 purchase totals =	$838.71		$932.6579	$932.66	$932.65	$932.60