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	$190.55	11.863%	$213.1549	$213.15	$213.15	$213.20
Purchase #2	$75.61	9.842%	$83.0515	$83.05	$83.05	$83.10
Purchase #3	$140.64	3.471%	$145.5216	$145.52	$145.50	$145.50
Purchase #4	$81.86	10.592%	$90.5306	$90.53	$90.55	$90.50
Purchase #5	$43.49	10.273%	$47.9577	$47.96	$47.95	$48.00
Purchase #6	$232.83	7.829%	$251.0583	$251.06	$251.05	$251.10
Purchase #7	$30.91	8.728%	$33.6078	$33.61	$33.60	$33.60
7 purchase totals =	$795.89		$864.8824	$864.88	$864.85	$865.00