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	$17.29	4.676%	$18.0985	$18.10	$18.10	$18.10
Purchase #2	$10.27	12.166%	$11.5194	$11.52	$11.50	$11.50
Purchase #3	$74.60	4.861%	$78.2263	$78.23	$78.25	$78.20
Purchase #4	$238.28	5.405%	$251.159	$251.16	$251.15	$251.20
Purchase #5	$82.96	9.136%	$90.5392	$90.54	$90.55	$90.50
Purchase #6	$186.37	8.551%	$202.3065	$202.31	$202.30	$202.30
Purchase #7	$123.50	8.141%	$133.5541	$133.55	$133.55	$133.60
7 purchase totals =	$733.27		$785.4030	$785.41	$785.40	$785.40