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	$10.83	3.190%	$11.1755	$11.18	$11.20	$11.20
Purchase #2	$130.82	9.123%	$142.7547	$142.75	$142.75	$142.80
Purchase #3	$250.41	10.491%	$276.6805	$276.68	$276.70	$276.70
Purchase #4	$192.83	3.367%	$199.3226	$199.32	$199.30	$199.30
Purchase #5	$41.91	4.299%	$43.7117	$43.71	$43.70	$43.70
Purchase #6	$200.76	10.801%	$222.4441	$222.44	$222.45	$222.40
Purchase #7	$244.28	13.347%	$276.8841	$276.88	$276.90	$276.90
7 purchase totals =	$1,071.84		$1,172.9732	$1,172.96	$1,173.00	$1,173.00