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	$207.95	4.549%	$217.4096	$217.41	$217.40	$217.40
Purchase #2	$222.79	6.490%	$237.2491	$237.25	$237.25	$237.20
Purchase #3	$74.41	12.358%	$83.6056	$83.61	$83.60	$83.60
Purchase #4	$203.48	9.350%	$222.5054	$222.51	$222.50	$222.50
Purchase #5	$22.35	9.637%	$24.5039	$24.50	$24.50	$24.50
Purchase #6	$43.84	4.523%	$45.8229	$45.82	$45.80	$45.80
Purchase #7	$160.35	6.841%	$171.3195	$171.32	$171.30	$171.30
7 purchase totals =	$935.17		$1,002.4160	$1,002.42	$1,002.35	$1,002.30