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	$66.76	10.738%	$73.9287	$73.93	$73.95	$73.90
Purchase #2	$248.79	5.214%	$261.7619	$261.76	$261.75	$261.80
Purchase #3	$78.78	4.492%	$82.3188	$82.32	$82.30	$82.30
Purchase #4	$45.29	9.518%	$49.6007	$49.60	$49.60	$49.60
Purchase #5	$227.41	5.685%	$240.3383	$240.34	$240.35	$240.30
Purchase #6	$216.41	10.209%	$238.5033	$238.50	$238.50	$238.50
Purchase #7	$89.93	3.321%	$92.9166	$92.92	$92.90	$92.90
7 purchase totals =	$973.37		$1,039.3683	$1,039.37	$1,039.35	$1,039.30