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	$204.53	11.294%	$227.6296	$227.63	$227.65	$227.60
Purchase #2	$141.92	5.751%	$150.0818	$150.08	$150.10	$150.10
Purchase #3	$112.87	3.223%	$116.5078	$116.51	$116.50	$116.50
Purchase #4	$198.76	13.544%	$225.6801	$225.68	$225.70	$225.70
Purchase #5	$153.65	4.468%	$160.5151	$160.52	$160.50	$160.50
Purchase #6	$33.81	9.503%	$37.023	$37.02	$37.00	$37.00
Purchase #7	$144.74	12.192%	$162.3867	$162.39	$162.40	$162.40
7 purchase totals =	$990.28		$1,079.8241	$1,079.83	$1,079.85	$1,079.80