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	$230.72	13.321%	$261.4542	$261.45	$261.45	$261.50
Purchase #2	$193.88	12.446%	$218.0103	$218.01	$218.00	$218.00
Purchase #3	$82.46	8.754%	$89.6785	$89.68	$89.70	$89.70
Purchase #4	$178.70	7.440%	$191.9953	$192.00	$192.00	$192.00
Purchase #5	$198.25	12.421%	$222.8746	$222.87	$222.85	$222.90
Purchase #6	$87.82	6.416%	$93.4545	$93.45	$93.45	$93.50
Purchase #7	$79.54	4.142%	$82.8345	$82.83	$82.85	$82.80
7 purchase totals =	$1,051.37		$1,160.3019	$1,160.29	$1,160.30	$1,160.40