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	$209.75	13.337%	$237.7244	$237.72	$237.70	$237.70
Purchase #2	$182.66	6.354%	$194.2662	$194.27	$194.25	$194.30
Purchase #3	$70.66	3.205%	$72.9247	$72.92	$72.90	$72.90
Purchase #4	$51.69	9.865%	$56.7892	$56.79	$56.80	$56.80
Purchase #5	$150.73	10.363%	$166.3501	$166.35	$166.35	$166.40
Purchase #6	$164.78	10.546%	$182.1577	$182.16	$182.15	$182.20
Purchase #7	$76.51	5.229%	$80.5107	$80.51	$80.50	$80.50
7 purchase totals =	$906.78		$990.7230	$990.72	$990.65	$990.80