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	$85.44	5.688%	$90.2998	$90.30	$90.30	$90.30
Purchase #2	$156.93	5.417%	$165.4309	$165.43	$165.45	$165.40
Purchase #3	$92.60	10.360%	$102.1934	$102.19	$102.20	$102.20
Purchase #4	$219.56	5.702%	$232.0793	$232.08	$232.10	$232.10
Purchase #5	$208.67	12.378%	$234.4992	$234.50	$234.50	$234.50
Purchase #6	$138.38	12.817%	$156.1162	$156.12	$156.10	$156.10
Purchase #7	$84.48	5.671%	$89.2709	$89.27	$89.25	$89.30
7 purchase totals =	$986.06		$1,069.8897	$1,069.89	$1,069.90	$1,069.90