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	$162.35	10.584%	$179.5331	$179.53	$179.55	$179.50
Purchase #2	$69.78	12.645%	$78.6037	$78.60	$78.60	$78.60
Purchase #3	$233.32	11.481%	$260.1075	$260.11	$260.10	$260.10
Purchase #4	$81.28	13.308%	$92.0967	$92.10	$92.10	$92.10
Purchase #5	$62.30	3.533%	$64.5011	$64.50	$64.50	$64.50
Purchase #6	$127.34	8.717%	$138.4402	$138.44	$138.45	$138.40
Purchase #7	$150.30	5.228%	$158.1577	$158.16	$158.15	$158.20
7 purchase totals =	$886.67		$971.4400	$971.44	$971.45	$971.40