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	$14.69	10.439%	$16.2235	$16.22	$16.20	$16.20
Purchase #2	$35.50	5.280%	$37.3744	$37.37	$37.35	$37.40
Purchase #3	$233.49	12.179%	$261.9267	$261.93	$261.95	$261.90
Purchase #4	$205.38	6.379%	$218.4812	$218.48	$218.50	$218.50
Purchase #5	$118.29	10.299%	$130.4727	$130.47	$130.45	$130.50
Purchase #6	$200.58	10.721%	$222.0842	$222.08	$222.10	$222.10
Purchase #7	$64.92	10.508%	$71.7418	$71.74	$71.75	$71.70
7 purchase totals =	$872.85		$958.3045	$958.29	$958.30	$958.30