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	$167.35	11.296%	$186.2539	$186.25	$186.25	$186.30
Purchase #2	$196.69	4.575%	$205.6886	$205.69	$205.70	$205.70
Purchase #3	$56.69	4.468%	$59.2229	$59.22	$59.20	$59.20
Purchase #4	$11.69	5.436%	$12.3255	$12.33	$12.35	$12.30
Purchase #5	$40.80	11.683%	$45.5667	$45.57	$45.55	$45.60
Purchase #6	$213.68	5.227%	$224.8491	$224.85	$224.85	$224.80
Purchase #7	$123.30	5.370%	$129.9212	$129.92	$129.90	$129.90
7 purchase totals =	$810.20		$863.8279	$863.83	$863.80	$863.80