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	$174.90	8.808%	$190.3052	$190.31	$190.30	$190.30
Purchase #2	$104.86	13.265%	$118.7697	$118.77	$118.75	$118.80
Purchase #3	$41.30	13.328%	$46.8045	$46.80	$46.80	$46.80
Purchase #4	$16.36	13.297%	$18.5354	$18.54	$18.55	$18.50
Purchase #5	$83.93	4.645%	$87.8285	$87.83	$87.85	$87.80
Purchase #6	$53.49	3.658%	$55.4467	$55.45	$55.45	$55.40
Purchase #7	$89.32	4.403%	$93.2528	$93.25	$93.25	$93.30
7 purchase totals =	$564.16		$610.9428	$610.95	$610.95	$610.90