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	$163.54	12.545%	$184.0561	$184.06	$184.05	$184.10
Purchase #2	$191.72	9.555%	$210.0388	$210.04	$210.05	$210.00
Purchase #3	$231.82	4.812%	$242.9752	$242.98	$243.00	$243.00
Purchase #4	$134.57	8.752%	$146.3476	$146.35	$146.35	$146.30
Purchase #5	$216.89	7.705%	$233.6014	$233.60	$233.60	$233.60
Purchase #6	$250.81	11.665%	$280.067	$280.07	$280.05	$280.10
Purchase #7	$33.67	13.470%	$38.2053	$38.21	$38.20	$38.20
7 purchase totals =	$1,223.02		$1,335.2914	$1,335.31	$1,335.30	$1,335.30