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	$102.51	13.236%	$116.0782	$116.08	$116.10	$116.10
Purchase #2	$94.59	6.466%	$100.7062	$100.71	$100.70	$100.70
Purchase #3	$33.78	9.646%	$37.0384	$37.04	$37.05	$37.00
Purchase #4	$63.82	11.284%	$71.0214	$71.02	$71.00	$71.00
Purchase #5	$187.74	7.393%	$201.6196	$201.62	$201.60	$201.60
Purchase #6	$179.44	6.457%	$191.0264	$191.03	$191.05	$191.00
Purchase #7	$139.73	10.450%	$154.3318	$154.33	$154.35	$154.30
7 purchase totals =	$801.61		$871.8220	$871.83	$871.85	$871.70