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	$121.59	7.403%	$130.5913	$130.59	$130.60	$130.60
Purchase #2	$246.57	3.243%	$254.5663	$254.57	$254.55	$254.60
Purchase #3	$16.25	13.459%	$18.4371	$18.44	$18.45	$18.40
Purchase #4	$218.42	13.821%	$248.6078	$248.61	$248.60	$248.60
Purchase #5	$133.78	10.163%	$147.3761	$147.38	$147.40	$147.40
Purchase #6	$194.81	12.551%	$219.2606	$219.26	$219.25	$219.30
Purchase #7	$56.48	4.873%	$59.2323	$59.23	$59.25	$59.20
7 purchase totals =	$987.90		$1,078.0715	$1,078.08	$1,078.10	$1,078.10