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	$220.72	7.430%	$237.1195	$237.12	$237.10	$237.10
Purchase #2	$103.99	11.736%	$116.1943	$116.19	$116.20	$116.20
Purchase #3	$190.57	4.365%	$198.8884	$198.89	$198.90	$198.90
Purchase #4	$191.81	8.725%	$208.5454	$208.55	$208.55	$208.50
Purchase #5	$89.29	13.856%	$101.662	$101.66	$101.65	$101.70
Purchase #6	$188.30	13.589%	$213.8881	$213.89	$213.90	$213.90
Purchase #7	$45.53	11.633%	$50.8265	$50.83	$50.85	$50.80
7 purchase totals =	$1,030.21		$1,127.1242	$1,127.13	$1,127.15	$1,127.10