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	$250.80	10.216%	$276.4217	$276.42	$276.40	$276.40
Purchase #2	$68.80	11.653%	$76.8173	$76.82	$76.80	$76.80
Purchase #3	$126.43	10.616%	$139.8518	$139.85	$139.85	$139.90
Purchase #4	$50.77	10.226%	$55.9617	$55.96	$55.95	$56.00
Purchase #5	$202.43	6.394%	$215.3734	$215.37	$215.35	$215.40
Purchase #6	$63.92	12.622%	$71.988	$71.99	$72.00	$72.00
Purchase #7	$228.33	8.826%	$248.4824	$248.48	$248.50	$248.50
7 purchase totals =	$991.48		$1,084.8963	$1,084.89	$1,084.85	$1,085.00