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	$75.77	8.385%	$82.1233	$82.12	$82.10	$82.10
Purchase #2	$207.97	11.356%	$231.5871	$231.59	$231.60	$231.60
Purchase #3	$130.38	9.162%	$142.3254	$142.33	$142.35	$142.30
Purchase #4	$163.52	6.123%	$173.5323	$173.53	$173.55	$173.50
Purchase #5	$18.36	10.746%	$20.333	$20.33	$20.35	$20.30
Purchase #6	$134.33	4.733%	$140.6878	$140.69	$140.70	$140.70
Purchase #7	$231.79	3.730%	$240.4358	$240.44	$240.45	$240.40
7 purchase totals =	$962.12		$1,031.0247	$1,031.03	$1,031.10	$1,030.90