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	$206.93	4.290%	$215.8073	$215.81	$215.80	$215.80
Purchase #2	$172.74	5.255%	$181.8175	$181.82	$181.80	$181.80
Purchase #3	$156.33	13.125%	$176.8483	$176.85	$176.85	$176.80
Purchase #4	$31.87	6.552%	$33.9581	$33.96	$33.95	$34.00
Purchase #5	$168.35	4.696%	$176.2557	$176.26	$176.25	$176.30
Purchase #6	$66.70	8.433%	$72.3248	$72.32	$72.30	$72.30
Purchase #7	$219.46	3.542%	$227.2333	$227.23	$227.25	$227.20
7 purchase totals =	$1,022.38		$1,084.2450	$1,084.25	$1,084.20	$1,084.20