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	$32.83	13.699%	$37.3274	$37.33	$37.35	$37.30
Purchase #2	$160.94	4.172%	$167.6544	$167.65	$167.65	$167.70
Purchase #3	$163.38	11.371%	$181.9579	$181.96	$181.95	$182.00
Purchase #4	$146.85	7.315%	$157.5921	$157.59	$157.60	$157.60
Purchase #5	$186.34	5.410%	$196.421	$196.42	$196.40	$196.40
Purchase #6	$164.67	12.139%	$184.6593	$184.66	$184.65	$184.70
Purchase #7	$243.46	5.302%	$256.3682	$256.37	$256.35	$256.40
7 purchase totals =	$1,098.47		$1,181.9803	$1,181.98	$1,181.95	$1,182.10