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	$137.87	11.167%	$153.2659	$153.27	$153.25	$153.30
Purchase #2	$77.77	7.318%	$83.4612	$83.46	$83.45	$83.50
Purchase #3	$239.74	5.676%	$253.3476	$253.35	$253.35	$253.30
Purchase #4	$234.50	8.825%	$255.1946	$255.19	$255.20	$255.20
Purchase #5	$102.62	8.535%	$111.3786	$111.38	$111.40	$111.40
Purchase #6	$122.90	10.130%	$135.3498	$135.35	$135.35	$135.30
Purchase #7	$164.83	9.180%	$179.9614	$179.96	$179.95	$180.00
7 purchase totals =	$1,080.23		$1,171.9591	$1,171.96	$1,171.95	$1,172.00