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	$93.63	7.268%	$100.435	$100.44	$100.45	$100.40
Purchase #2	$123.65	6.688%	$131.9197	$131.92	$131.90	$131.90
Purchase #3	$26.74	9.611%	$29.31	$29.31	$29.30	$29.30
Purchase #4	$164.37	6.158%	$174.4919	$174.49	$174.50	$174.50
Purchase #5	$247.53	8.216%	$267.8671	$267.87	$267.85	$267.90
Purchase #6	$191.76	4.493%	$200.3758	$200.38	$200.40	$200.40
Purchase #7	$44.47	12.452%	$50.0074	$50.01	$50.00	$50.00
7 purchase totals =	$892.15		$954.4069	$954.42	$954.40	$954.40