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	$37.52	11.789%	$41.9432	$41.94	$41.95	$41.90
Purchase #2	$22.34	6.653%	$23.8263	$23.83	$23.85	$23.80
Purchase #3	$237.83	11.549%	$265.297	$265.30	$265.30	$265.30
Purchase #4	$144.80	13.321%	$164.0888	$164.09	$164.10	$164.10
Purchase #5	$210.56	9.637%	$230.8517	$230.85	$230.85	$230.90
Purchase #6	$65.85	9.856%	$72.3402	$72.34	$72.35	$72.30
Purchase #7	$202.49	3.537%	$209.6521	$209.65	$209.65	$209.70
7 purchase totals =	$921.39		$1,007.9993	$1,008.00	$1,008.05	$1,008.00