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	$162.78	8.215%	$176.1524	$176.15	$176.15	$176.20
Purchase #2	$126.53	3.501%	$130.9598	$130.96	$130.95	$131.00
Purchase #3	$179.87	5.508%	$189.7772	$189.78	$189.80	$189.80
Purchase #4	$172.39	13.704%	$196.0143	$196.01	$196.00	$196.00
Purchase #5	$108.94	11.154%	$121.0912	$121.09	$121.10	$121.10
Purchase #6	$222.90	9.155%	$243.3065	$243.31	$243.30	$243.30
Purchase #7	$40.40	5.264%	$42.5267	$42.53	$42.55	$42.50
7 purchase totals =	$1,013.81		$1,099.8281	$1,099.83	$1,099.85	$1,099.90