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	$28.59	7.625%	$30.77	$30.77	$30.75	$30.80
Purchase #2	$227.83	12.221%	$255.6731	$255.67	$255.65	$255.70
Purchase #3	$205.47	8.195%	$222.3083	$222.31	$222.30	$222.30
Purchase #4	$240.42	10.487%	$265.6328	$265.63	$265.65	$265.60
Purchase #5	$194.83	12.746%	$219.663	$219.66	$219.65	$219.70
Purchase #6	$13.63	8.580%	$14.7995	$14.80	$14.80	$14.80
Purchase #7	$61.96	9.479%	$67.8332	$67.83	$67.85	$67.80
7 purchase totals =	$972.73		$1,076.6799	$1,076.67	$1,076.65	$1,076.70