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	$250.89	9.361%	$274.3758	$274.38	$274.40	$274.40
Purchase #2	$38.29	7.333%	$41.0978	$41.10	$41.10	$41.10
Purchase #3	$142.95	7.257%	$153.3239	$153.32	$153.30	$153.30
Purchase #4	$82.55	12.672%	$93.0107	$93.01	$93.00	$93.00
Purchase #5	$50.59	7.190%	$54.2274	$54.23	$54.25	$54.20
Purchase #6	$164.38	13.131%	$185.9647	$185.96	$185.95	$186.00
Purchase #7	$141.31	11.103%	$156.9996	$157.00	$157.00	$157.00
7 purchase totals =	$870.96		$958.9999	$959.00	$959.00	$959.00