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	$136.42	13.231%	$154.4697	$154.47	$154.45	$154.50
Purchase #2	$179.55	3.385%	$185.6278	$185.63	$185.65	$185.60
Purchase #3	$52.84	3.847%	$54.8728	$54.87	$54.85	$54.90
Purchase #4	$190.50	11.518%	$212.4418	$212.44	$212.45	$212.40
Purchase #5	$87.47	6.704%	$93.334	$93.33	$93.35	$93.30
Purchase #6	$198.32	8.577%	$215.3299	$215.33	$215.35	$215.30
Purchase #7	$165.90	9.559%	$181.7584	$181.76	$181.75	$181.80
7 purchase totals =	$1,011.00		$1,097.8344	$1,097.83	$1,097.85	$1,097.80