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	$182.99	7.552%	$196.8094	$196.81	$196.80	$196.80
Purchase #2	$20.73	10.419%	$22.8899	$22.89	$22.90	$22.90
Purchase #3	$239.92	12.375%	$269.6101	$269.61	$269.60	$269.60
Purchase #4	$129.43	8.731%	$140.7305	$140.73	$140.75	$140.70
Purchase #5	$233.70	11.809%	$261.2976	$261.30	$261.30	$261.30
Purchase #6	$116.70	3.217%	$120.4542	$120.45	$120.45	$120.50
Purchase #7	$127.90	13.110%	$144.6677	$144.67	$144.65	$144.70
7 purchase totals =	$1,051.37		$1,156.4594	$1,156.46	$1,156.45	$1,156.50