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	$158.62	8.297%	$171.7807	$171.78	$171.80	$171.80
Purchase #2	$116.62	12.393%	$131.0727	$131.07	$131.05	$131.10
Purchase #3	$208.51	3.352%	$215.4993	$215.50	$215.50	$215.50
Purchase #4	$112.34	3.767%	$116.5718	$116.57	$116.55	$116.60
Purchase #5	$127.84	6.617%	$136.2992	$136.30	$136.30	$136.30
Purchase #6	$190.37	4.404%	$198.7539	$198.75	$198.75	$198.80
Purchase #7	$87.28	3.269%	$90.1332	$90.13	$90.15	$90.10
7 purchase totals =	$1,001.58		$1,060.1108	$1,060.10	$1,060.10	$1,060.20