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	$156.71	11.635%	$174.9432	$174.94	$174.95	$174.90
Purchase #2	$130.50	6.542%	$139.0373	$139.04	$139.05	$139.00
Purchase #3	$186.75	4.712%	$195.5497	$195.55	$195.55	$195.50
Purchase #4	$233.55	9.497%	$255.7302	$255.73	$255.75	$255.70
Purchase #5	$37.52	12.106%	$42.0622	$42.06	$42.05	$42.10
Purchase #6	$51.56	12.210%	$57.8555	$57.86	$57.85	$57.90
Purchase #7	$34.55	7.403%	$37.1077	$37.11	$37.10	$37.10
7 purchase totals =	$831.14		$902.2858	$902.29	$902.30	$902.20