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	$43.99	13.872%	$50.0923	$50.09	$50.10	$50.10
Purchase #2	$28.98	7.725%	$31.2187	$31.22	$31.20	$31.20
Purchase #3	$67.60	5.708%	$71.4586	$71.46	$71.45	$71.50
Purchase #4	$50.47	13.554%	$57.3107	$57.31	$57.30	$57.30
Purchase #5	$213.54	6.812%	$228.0863	$228.09	$228.10	$228.10
Purchase #6	$226.27	6.752%	$241.5478	$241.55	$241.55	$241.50
Purchase #7	$94.51	5.330%	$99.5474	$99.55	$99.55	$99.50
7 purchase totals =	$725.36		$779.2618	$779.27	$779.25	$779.20