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	$165.53	13.396%	$187.7044	$187.70	$187.70	$187.70
Purchase #2	$250.72	11.861%	$280.4579	$280.46	$280.45	$280.50
Purchase #3	$83.80	12.642%	$94.394	$94.39	$94.40	$94.40
Purchase #4	$108.35	7.268%	$116.2249	$116.22	$116.20	$116.20
Purchase #5	$240.52	11.505%	$268.1918	$268.19	$268.20	$268.20
Purchase #6	$37.59	13.421%	$42.635	$42.64	$42.65	$42.60
Purchase #7	$185.84	12.347%	$208.7857	$208.79	$208.80	$208.80
7 purchase totals =	$1,072.35		$1,198.3937	$1,198.39	$1,198.40	$1,198.40