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	$104.53	13.437%	$118.5757	$118.58	$118.60	$118.60
Purchase #2	$247.39	5.547%	$261.1127	$261.11	$261.10	$261.10
Purchase #3	$247.63	13.410%	$280.8372	$280.84	$280.85	$280.80
Purchase #4	$162.63	9.527%	$178.1238	$178.12	$178.10	$178.10
Purchase #5	$151.36	13.665%	$172.0433	$172.04	$172.05	$172.00
Purchase #6	$89.34	3.557%	$92.5178	$92.52	$92.50	$92.50
Purchase #7	$131.99	7.866%	$142.3723	$142.37	$142.35	$142.40
7 purchase totals =	$1,134.87		$1,245.5828	$1,245.58	$1,245.55	$1,245.50