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	$242.91	10.749%	$269.0204	$269.02	$269.00	$269.00
Purchase #2	$105.89	5.350%	$111.5551	$111.56	$111.55	$111.60
Purchase #3	$54.99	5.707%	$58.1283	$58.13	$58.15	$58.10
Purchase #4	$39.74	3.547%	$41.1496	$41.15	$41.15	$41.10
Purchase #5	$28.88	7.873%	$31.1537	$31.15	$31.15	$31.20
Purchase #6	$217.84	12.845%	$245.8215	$245.82	$245.80	$245.80
Purchase #7	$97.74	13.590%	$111.0229	$111.02	$111.00	$111.00
7 purchase totals =	$787.99		$867.8515	$867.85	$867.80	$867.80