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	$243.98	6.315%	$259.3873	$259.39	$259.40	$259.40
Purchase #2	$177.69	10.293%	$195.9796	$195.98	$196.00	$196.00
Purchase #3	$65.41	9.319%	$71.5056	$71.51	$71.50	$71.50
Purchase #4	$107.61	8.365%	$116.6116	$116.61	$116.60	$116.60
Purchase #5	$124.55	8.132%	$134.6784	$134.68	$134.70	$134.70
Purchase #6	$83.54	10.504%	$92.315	$92.32	$92.30	$92.30
Purchase #7	$192.67	12.269%	$216.3087	$216.31	$216.30	$216.30
7 purchase totals =	$995.45		$1,086.7862	$1,086.80	$1,086.80	$1,086.80