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	$169.79	9.111%	$185.2596	$185.26	$185.25	$185.30
Purchase #2	$166.69	10.817%	$184.7209	$184.72	$184.70	$184.70
Purchase #3	$244.94	13.469%	$277.931	$277.93	$277.95	$277.90
Purchase #4	$50.55	12.740%	$56.9901	$56.99	$57.00	$57.00
Purchase #5	$43.60	8.193%	$47.1721	$47.17	$47.15	$47.20
Purchase #6	$187.32	7.246%	$200.8932	$200.89	$200.90	$200.90
Purchase #7	$60.43	9.839%	$66.3757	$66.38	$66.40	$66.40
7 purchase totals =	$923.32		$1,019.3426	$1,019.34	$1,019.35	$1,019.40