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	$204.57	6.734%	$218.3457	$218.35	$218.35	$218.30
Purchase #2	$171.82	11.465%	$191.5192	$191.52	$191.50	$191.50
Purchase #3	$30.52	5.119%	$32.0823	$32.08	$32.10	$32.10
Purchase #4	$222.54	3.691%	$230.754	$230.75	$230.75	$230.80
Purchase #5	$112.44	11.470%	$125.3369	$125.34	$125.35	$125.30
Purchase #6	$99.37	6.150%	$105.4813	$105.48	$105.50	$105.50
Purchase #7	$169.77	4.403%	$177.245	$177.25	$177.25	$177.20
7 purchase totals =	$1,011.03		$1,080.7644	$1,080.77	$1,080.80	$1,080.70