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	$187.90	6.209%	$199.5667	$199.57	$199.55	$199.60
Purchase #2	$107.65	7.554%	$115.7819	$115.78	$115.80	$115.80
Purchase #3	$185.71	3.208%	$191.6676	$191.67	$191.65	$191.70
Purchase #4	$198.41	12.332%	$222.8779	$222.88	$222.90	$222.90
Purchase #5	$78.80	8.149%	$85.2214	$85.22	$85.20	$85.20
Purchase #6	$215.49	10.150%	$237.3622	$237.36	$237.35	$237.40
Purchase #7	$86.42	5.607%	$91.2656	$91.27	$91.25	$91.30
7 purchase totals =	$1,060.38		$1,143.7433	$1,143.75	$1,143.70	$1,143.90