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	$217.47	7.166%	$233.0539	$233.05	$233.05	$233.10
Purchase #2	$194.77	9.665%	$213.5945	$213.59	$213.60	$213.60
Purchase #3	$209.37	13.127%	$236.854	$236.85	$236.85	$236.90
Purchase #4	$34.86	6.865%	$37.2531	$37.25	$37.25	$37.30
Purchase #5	$185.44	5.709%	$196.0268	$196.03	$196.05	$196.00
Purchase #6	$205.31	8.698%	$223.1679	$223.17	$223.15	$223.20
Purchase #7	$123.63	13.408%	$140.2063	$140.21	$140.20	$140.20
7 purchase totals =	$1,170.85		$1,280.1565	$1,280.15	$1,280.15	$1,280.30