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	$92.64	10.756%	$102.6044	$102.60	$102.60	$102.60
Purchase #2	$143.28	9.519%	$156.9188	$156.92	$156.90	$156.90
Purchase #3	$76.46	5.801%	$80.8954	$80.90	$80.90	$80.90
Purchase #4	$184.48	7.596%	$198.4931	$198.49	$198.50	$198.50
Purchase #5	$142.82	6.492%	$152.0919	$152.09	$152.10	$152.10
Purchase #6	$170.69	3.254%	$176.2443	$176.24	$176.25	$176.20
Purchase #7	$73.36	7.178%	$78.6258	$78.63	$78.65	$78.60
7 purchase totals =	$883.73		$945.8737	$945.87	$945.90	$945.80