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	$12.59	6.765%	$13.4417	$13.44	$13.45	$13.40
Purchase #2	$179.83	10.253%	$198.268	$198.27	$198.25	$198.30
Purchase #3	$241.41	8.172%	$261.138	$261.14	$261.15	$261.10
Purchase #4	$172.81	5.359%	$182.0709	$182.07	$182.05	$182.10
Purchase #5	$47.97	7.536%	$51.585	$51.59	$51.60	$51.60
Purchase #6	$50.91	11.413%	$56.7204	$56.72	$56.70	$56.70
Purchase #7	$90.60	10.263%	$99.8983	$99.90	$99.90	$99.90
7 purchase totals =	$796.12		$863.1223	$863.13	$863.10	$863.10