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	$27.41	7.355%	$29.426	$29.43	$29.45	$29.40
Purchase #2	$171.91	5.350%	$181.1072	$181.11	$181.10	$181.10
Purchase #3	$92.78	5.549%	$97.9284	$97.93	$97.95	$97.90
Purchase #4	$68.67	4.807%	$71.971	$71.97	$71.95	$72.00
Purchase #5	$37.82	10.119%	$41.647	$41.65	$41.65	$41.60
Purchase #6	$141.94	7.456%	$152.523	$152.52	$152.50	$152.50
Purchase #7	$143.88	4.403%	$150.215	$150.22	$150.20	$150.20
7 purchase totals =	$684.41		$724.8176	$724.83	$724.80	$724.70