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	$114.72	10.462%	$126.722	$126.72	$126.70	$126.70
Purchase #2	$247.37	10.592%	$273.5714	$273.57	$273.55	$273.60
Purchase #3	$99.82	9.386%	$109.1891	$109.19	$109.20	$109.20
Purchase #4	$247.72	5.559%	$261.4908	$261.49	$261.50	$261.50
Purchase #5	$117.91	3.107%	$121.5735	$121.57	$121.55	$121.60
Purchase #6	$78.39	5.521%	$82.7179	$82.72	$82.70	$82.70
Purchase #7	$38.25	12.743%	$43.1242	$43.12	$43.10	$43.10
7 purchase totals =	$944.18		$1,018.3889	$1,018.38	$1,018.30	$1,018.40