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	$40.30	4.104%	$41.9539	$41.95	$41.95	$42.00
Purchase #2	$183.55	6.849%	$196.1213	$196.12	$196.10	$196.10
Purchase #3	$219.87	8.124%	$237.7322	$237.73	$237.75	$237.70
Purchase #4	$43.94	5.785%	$46.4819	$46.48	$46.50	$46.50
Purchase #5	$92.37	9.231%	$100.8967	$100.90	$100.90	$100.90
Purchase #6	$217.35	11.649%	$242.6691	$242.67	$242.65	$242.70
Purchase #7	$250.52	4.558%	$261.9387	$261.94	$261.95	$261.90
7 purchase totals =	$1,047.90		$1,127.7938	$1,127.79	$1,127.80	$1,127.80