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	$203.59	3.746%	$211.2165	$211.22	$211.20	$211.20
Purchase #2	$40.77	11.605%	$45.5014	$45.50	$45.50	$45.50
Purchase #3	$151.96	11.507%	$169.446	$169.45	$169.45	$169.40
Purchase #4	$36.92	5.447%	$38.931	$38.93	$38.95	$38.90
Purchase #5	$6.80	6.718%	$7.2568	$7.26	$7.25	$7.30
Purchase #6	$90.48	6.142%	$96.0373	$96.04	$96.05	$96.00
Purchase #7	$181.72	9.829%	$199.5813	$199.58	$199.60	$199.60
7 purchase totals =	$712.24		$767.9703	$767.98	$768.00	$767.90