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	$118.41	11.221%	$131.6968	$131.70	$131.70	$131.70
Purchase #2	$101.44	12.601%	$114.2225	$114.22	$114.20	$114.20
Purchase #3	$53.65	11.286%	$59.7049	$59.70	$59.70	$59.70
Purchase #4	$75.82	9.104%	$82.7227	$82.72	$82.70	$82.70
Purchase #5	$87.46	9.663%	$95.9113	$95.91	$95.90	$95.90
Purchase #6	$246.93	13.574%	$280.4483	$280.45	$280.45	$280.40
Purchase #7	$236.52	10.446%	$261.2269	$261.23	$261.25	$261.20
7 purchase totals =	$920.23		$1,025.9334	$1,025.93	$1,025.90	$1,025.80