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	$249.27	10.835%	$276.2784	$276.28	$276.30	$276.30
Purchase #2	$193.38	11.353%	$215.3344	$215.33	$215.35	$215.30
Purchase #3	$187.33	10.442%	$206.891	$206.89	$206.90	$206.90
Purchase #4	$104.28	3.497%	$107.9267	$107.93	$107.95	$107.90
Purchase #5	$90.98	4.255%	$94.8512	$94.85	$94.85	$94.90
Purchase #6	$63.46	6.172%	$67.3768	$67.38	$67.40	$67.40
Purchase #7	$82.43	6.196%	$87.5374	$87.54	$87.55	$87.50
7 purchase totals =	$971.13		$1,056.1959	$1,056.20	$1,056.30	$1,056.20