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	$219.60	9.450%	$240.3522	$240.35	$240.35	$240.40
Purchase #2	$38.38	5.118%	$40.3443	$40.34	$40.35	$40.30
Purchase #3	$22.71	13.830%	$25.8508	$25.85	$25.85	$25.90
Purchase #4	$246.50	4.213%	$256.885	$256.89	$256.90	$256.90
Purchase #5	$174.41	11.131%	$193.8236	$193.82	$193.80	$193.80
Purchase #6	$246.98	13.429%	$280.1469	$280.15	$280.15	$280.10
Purchase #7	$145.89	5.436%	$153.8206	$153.82	$153.80	$153.80
7 purchase totals =	$1,094.47		$1,191.2234	$1,191.22	$1,191.20	$1,191.20