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	$108.83	12.759%	$122.7156	$122.72	$122.70	$122.70
Purchase #2	$7.31	8.162%	$7.9066	$7.91	$7.90	$7.90
Purchase #3	$32.27	3.849%	$33.5121	$33.51	$33.50	$33.50
Purchase #4	$229.70	4.814%	$240.7578	$240.76	$240.75	$240.80
Purchase #5	$233.89	12.362%	$262.8035	$262.80	$262.80	$262.80
Purchase #6	$182.44	4.509%	$190.6662	$190.67	$190.65	$190.70
Purchase #7	$250.37	7.621%	$269.4507	$269.45	$269.45	$269.50
7 purchase totals =	$1,044.81		$1,127.8125	$1,127.82	$1,127.75	$1,127.90