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	$152.85	13.142%	$172.9375	$172.94	$172.95	$172.90
Purchase #2	$181.44	8.237%	$196.3852	$196.39	$196.40	$196.40
Purchase #3	$24.62	10.832%	$27.2868	$27.29	$27.30	$27.30
Purchase #4	$180.68	5.777%	$191.1179	$191.12	$191.10	$191.10
Purchase #5	$14.60	8.766%	$15.8798	$15.88	$15.90	$15.90
Purchase #6	$136.49	7.855%	$147.2113	$147.21	$147.20	$147.20
Purchase #7	$99.69	12.474%	$112.1253	$112.13	$112.15	$112.10
7 purchase totals =	$790.37		$862.9438	$862.96	$863.00	$862.90