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	$101.95	13.680%	$115.8968	$115.90	$115.90	$115.90
Purchase #2	$19.33	12.225%	$21.6931	$21.69	$21.70	$21.70
Purchase #3	$180.56	5.363%	$190.2434	$190.24	$190.25	$190.20
Purchase #4	$226.60	4.753%	$237.3703	$237.37	$237.35	$237.40
Purchase #5	$200.45	11.181%	$222.8623	$222.86	$222.85	$222.90
Purchase #6	$59.71	5.116%	$62.7648	$62.76	$62.75	$62.80
Purchase #7	$145.70	3.175%	$150.326	$150.33	$150.35	$150.30
7 purchase totals =	$934.30		$1,001.1567	$1,001.15	$1,001.15	$1,001.20