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	$109.66	7.247%	$117.6071	$117.61	$117.60	$117.60
Purchase #2	$62.82	7.756%	$67.6923	$67.69	$67.70	$67.70
Purchase #3	$184.40	6.365%	$196.1371	$196.14	$196.15	$196.10
Purchase #4	$148.30	3.348%	$153.2651	$153.27	$153.25	$153.30
Purchase #5	$241.43	5.237%	$254.0737	$254.07	$254.05	$254.10
Purchase #6	$131.61	12.325%	$147.8309	$147.83	$147.85	$147.80
Purchase #7	$194.62	9.660%	$213.4203	$213.42	$213.40	$213.40
7 purchase totals =	$1,072.84		$1,150.0265	$1,150.03	$1,150.00	$1,150.00