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	$181.46	9.571%	$198.8275	$198.83	$198.85	$198.80
Purchase #2	$210.36	3.580%	$217.8909	$217.89	$217.90	$217.90
Purchase #3	$76.68	8.865%	$83.4777	$83.48	$83.50	$83.50
Purchase #4	$105.90	12.757%	$119.4097	$119.41	$119.40	$119.40
Purchase #5	$246.30	13.651%	$279.9224	$279.92	$279.90	$279.90
Purchase #6	$159.77	13.626%	$181.5403	$181.54	$181.55	$181.50
Purchase #7	$28.30	3.256%	$29.2214	$29.22	$29.20	$29.20
7 purchase totals =	$1,008.77		$1,110.2899	$1,110.29	$1,110.30	$1,110.20