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	$127.85	4.228%	$133.2555	$133.26	$133.25	$133.30
Purchase #2	$132.91	10.109%	$146.3459	$146.35	$146.35	$146.30
Purchase #3	$42.27	6.852%	$45.1663	$45.17	$45.15	$45.20
Purchase #4	$175.95	5.683%	$185.9492	$185.95	$185.95	$185.90
Purchase #5	$167.73	12.132%	$188.079	$188.08	$188.10	$188.10
Purchase #6	$175.91	6.140%	$186.7109	$186.71	$186.70	$186.70
Purchase #7	$159.65	8.756%	$173.629	$173.63	$173.65	$173.60
7 purchase totals =	$982.27		$1,059.1358	$1,059.15	$1,059.15	$1,059.10