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	$37.39	11.202%	$41.5784	$41.58	$41.60	$41.60
Purchase #2	$108.70	13.673%	$123.5626	$123.56	$123.55	$123.60
Purchase #3	$222.55	11.629%	$248.4303	$248.43	$248.45	$248.40
Purchase #4	$137.91	11.728%	$154.0841	$154.08	$154.10	$154.10
Purchase #5	$219.41	6.874%	$234.4922	$234.49	$234.50	$234.50
Purchase #6	$215.94	6.263%	$229.4643	$229.46	$229.45	$229.50
Purchase #7	$104.66	13.785%	$119.0874	$119.09	$119.10	$119.10
7 purchase totals =	$1,046.56		$1,150.6993	$1,150.69	$1,150.75	$1,150.80