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	$140.75	11.493%	$156.9264	$156.93	$156.95	$156.90
Purchase #2	$226.29	7.437%	$243.1192	$243.12	$243.10	$243.10
Purchase #3	$156.54	5.327%	$164.8789	$164.88	$164.90	$164.90
Purchase #4	$77.80	5.643%	$82.1903	$82.19	$82.20	$82.20
Purchase #5	$67.58	7.286%	$72.5039	$72.50	$72.50	$72.50
Purchase #6	$32.70	9.266%	$35.73	$35.73	$35.75	$35.70
Purchase #7	$41.32	6.124%	$43.8504	$43.85	$43.85	$43.90
7 purchase totals =	$742.98		$799.1991	$799.20	$799.25	$799.20