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	$159.73	13.644%	$181.5236	$181.52	$181.50	$181.50
Purchase #2	$171.32	3.591%	$177.4721	$177.47	$177.45	$177.50
Purchase #3	$12.76	3.202%	$13.1686	$13.17	$13.15	$13.20
Purchase #4	$56.85	8.522%	$61.6948	$61.69	$61.70	$61.70
Purchase #5	$152.52	11.134%	$169.5016	$169.50	$169.50	$169.50
Purchase #6	$108.67	8.475%	$117.8798	$117.88	$117.90	$117.90
Purchase #7	$54.35	13.351%	$61.6063	$61.61	$61.60	$61.60
7 purchase totals =	$716.20		$782.8468	$782.84	$782.80	$782.90