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	$144.90	11.837%	$162.0518	$162.05	$162.05	$162.10
Purchase #2	$241.89	9.651%	$265.2348	$265.23	$265.25	$265.20
Purchase #3	$15.41	6.828%	$16.4622	$16.46	$16.45	$16.50
Purchase #4	$166.89	10.187%	$183.8911	$183.89	$183.90	$183.90
Purchase #5	$161.84	8.857%	$176.1742	$176.17	$176.15	$176.20
Purchase #6	$250.96	9.815%	$275.5917	$275.59	$275.60	$275.60
Purchase #7	$137.93	9.118%	$150.5065	$150.51	$150.50	$150.50
7 purchase totals =	$1,119.82		$1,229.9123	$1,229.90	$1,229.90	$1,230.00