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	$202.29	13.369%	$229.3342	$229.33	$229.35	$229.30
Purchase #2	$41.50	8.367%	$44.9723	$44.97	$44.95	$45.00
Purchase #3	$113.42	5.322%	$119.4562	$119.46	$119.45	$119.50
Purchase #4	$116.65	10.142%	$128.4806	$128.48	$128.50	$128.50
Purchase #5	$121.46	7.453%	$130.5124	$130.51	$130.50	$130.50
Purchase #6	$245.47	5.370%	$258.6517	$258.65	$258.65	$258.70
Purchase #7	$181.77	3.760%	$188.6046	$188.60	$188.60	$188.60
7 purchase totals =	$1,022.56		$1,100.0120	$1,100.00	$1,100.00	$1,100.10