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	$225.91	12.630%	$254.4424	$254.44	$254.45	$254.40
Purchase #2	$211.98	6.818%	$226.4328	$226.43	$226.45	$226.40
Purchase #3	$202.53	7.353%	$217.422	$217.42	$217.40	$217.40
Purchase #4	$45.27	7.663%	$48.739	$48.74	$48.75	$48.70
Purchase #5	$122.63	7.171%	$131.4238	$131.42	$131.40	$131.40
Purchase #6	$86.34	10.646%	$95.5318	$95.53	$95.55	$95.50
Purchase #7	$36.95	13.426%	$41.9109	$41.91	$41.90	$41.90
7 purchase totals =	$931.61		$1,015.9027	$1,015.89	$1,015.90	$1,015.70