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	$237.49	3.432%	$245.6407	$245.64	$245.65	$245.60
Purchase #2	$111.74	12.766%	$126.0047	$126.00	$126.00	$126.00
Purchase #3	$186.39	7.183%	$199.7784	$199.78	$199.80	$199.80
Purchase #4	$52.32	8.566%	$56.8017	$56.80	$56.80	$56.80
Purchase #5	$38.59	12.286%	$43.3312	$43.33	$43.35	$43.30
Purchase #6	$67.39	5.199%	$70.8936	$70.89	$70.90	$70.90
Purchase #7	$82.73	9.710%	$90.7631	$90.76	$90.75	$90.80
7 purchase totals =	$776.65		$833.2134	$833.20	$833.25	$833.20