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	$172.82	13.475%	$196.1075	$196.11	$196.10	$196.10
Purchase #2	$161.53	13.554%	$183.4238	$183.42	$183.40	$183.40
Purchase #3	$66.32	10.142%	$73.0462	$73.05	$73.05	$73.00
Purchase #4	$38.44	9.558%	$42.1141	$42.11	$42.10	$42.10
Purchase #5	$86.94	9.270%	$94.9993	$95.00	$95.00	$95.00
Purchase #6	$141.70	8.568%	$153.8409	$153.84	$153.85	$153.80
Purchase #7	$41.50	5.142%	$43.6339	$43.63	$43.65	$43.60
7 purchase totals =	$709.25		$787.1657	$787.16	$787.15	$787.00