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	$90.61	11.404%	$100.9432	$100.94	$100.95	$100.90
Purchase #2	$169.55	13.209%	$191.9459	$191.95	$191.95	$191.90
Purchase #3	$6.95	6.697%	$7.4154	$7.42	$7.40	$7.40
Purchase #4	$67.96	7.252%	$72.8885	$72.89	$72.90	$72.90
Purchase #5	$163.31	3.379%	$168.8282	$168.83	$168.85	$168.80
Purchase #6	$107.70	11.160%	$119.7193	$119.72	$119.70	$119.70
Purchase #7	$213.68	9.681%	$234.3664	$234.37	$234.35	$234.40
7 purchase totals =	$819.76		$896.1069	$896.12	$896.10	$896.00