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	$198.94	9.776%	$218.3884	$218.39	$218.40	$218.40
Purchase #2	$177.62	3.156%	$183.2257	$183.23	$183.25	$183.20
Purchase #3	$40.93	12.606%	$46.0896	$46.09	$46.10	$46.10
Purchase #4	$166.94	11.313%	$185.8259	$185.83	$185.85	$185.80
Purchase #5	$73.44	10.870%	$81.4229	$81.42	$81.40	$81.40
Purchase #6	$53.25	11.762%	$59.5133	$59.51	$59.50	$59.50
Purchase #7	$231.65	12.164%	$259.8279	$259.83	$259.85	$259.80
7 purchase totals =	$942.77		$1,034.2937	$1,034.30	$1,034.35	$1,034.20