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	$31.93	13.215%	$36.1495	$36.15	$36.15	$36.10
Purchase #2	$43.26	7.582%	$46.54	$46.54	$46.55	$46.50
Purchase #3	$61.88	7.444%	$66.4863	$66.49	$66.50	$66.50
Purchase #4	$30.80	9.338%	$33.6761	$33.68	$33.70	$33.70
Purchase #5	$121.89	7.707%	$131.2841	$131.28	$131.30	$131.30
Purchase #6	$31.61	7.107%	$33.8565	$33.86	$33.85	$33.90
Purchase #7	$24.53	10.426%	$27.0875	$27.09	$27.10	$27.10
7 purchase totals =	$345.90		$375.0800	$375.09	$375.15	$375.10