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	$20.39	11.317%	$22.6975	$22.70	$22.70	$22.70
Purchase #2	$181.39	7.258%	$194.5553	$194.56	$194.55	$194.60
Purchase #3	$185.66	5.845%	$196.5118	$196.51	$196.50	$196.50
Purchase #4	$183.81	8.344%	$199.1471	$199.15	$199.15	$199.10
Purchase #5	$204.30	6.132%	$216.8277	$216.83	$216.85	$216.80
Purchase #6	$186.68	5.442%	$196.8391	$196.84	$196.85	$196.80
Purchase #7	$133.57	4.599%	$139.7129	$139.71	$139.70	$139.70
7 purchase totals =	$1,095.80		$1,166.2914	$1,166.30	$1,166.30	$1,166.20