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	$226.59	12.615%	$255.1743	$255.17	$255.15	$255.20
Purchase #2	$126.69	12.530%	$142.5643	$142.56	$142.55	$142.60
Purchase #3	$163.78	13.775%	$186.3407	$186.34	$186.35	$186.30
Purchase #4	$86.45	3.234%	$89.2458	$89.25	$89.25	$89.20
Purchase #5	$109.27	4.824%	$114.5412	$114.54	$114.55	$114.50
Purchase #6	$127.32	6.429%	$135.5054	$135.51	$135.50	$135.50
Purchase #7	$141.30	3.447%	$146.1706	$146.17	$146.15	$146.20
7 purchase totals =	$981.40		$1,069.5423	$1,069.54	$1,069.50	$1,069.50