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	$105.57	5.571%	$111.4513	$111.45	$111.45	$111.50
Purchase #2	$90.35	4.272%	$94.2098	$94.21	$94.20	$94.20
Purchase #3	$180.49	13.480%	$204.8201	$204.82	$204.80	$204.80
Purchase #4	$123.92	4.334%	$129.2907	$129.29	$129.30	$129.30
Purchase #5	$241.38	5.871%	$255.5514	$255.55	$255.55	$255.60
Purchase #6	$215.86	7.815%	$232.7295	$232.73	$232.75	$232.70
Purchase #7	$156.66	4.855%	$164.2658	$164.27	$164.25	$164.30
7 purchase totals =	$1,114.23		$1,192.3186	$1,192.32	$1,192.30	$1,192.40