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	$102.31	11.149%	$113.7165	$113.72	$113.70	$113.70
Purchase #2	$168.30	7.802%	$181.4308	$181.43	$181.45	$181.40
Purchase #3	$18.90	3.381%	$19.539	$19.54	$19.55	$19.50
Purchase #4	$10.30	5.682%	$10.8852	$10.89	$10.90	$10.90
Purchase #5	$82.76	9.398%	$90.5378	$90.54	$90.55	$90.50
Purchase #6	$21.94	3.311%	$22.6664	$22.67	$22.65	$22.70
Purchase #7	$176.94	5.489%	$186.6522	$186.65	$186.65	$186.70
7 purchase totals =	$581.45		$625.4279	$625.44	$625.45	$625.40