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	$159.25	4.873%	$167.0103	$167.01	$167.00	$167.00
Purchase #2	$240.36	5.602%	$253.825	$253.83	$253.85	$253.80
Purchase #3	$110.52	9.856%	$121.4129	$121.41	$121.40	$121.40
Purchase #4	$6.94	6.216%	$7.3714	$7.37	$7.35	$7.40
Purchase #5	$179.56	3.346%	$185.5681	$185.57	$185.55	$185.60
Purchase #6	$47.54	9.570%	$52.0896	$52.09	$52.10	$52.10
Purchase #7	$67.72	13.102%	$76.5927	$76.59	$76.60	$76.60
7 purchase totals =	$811.89		$863.8700	$863.87	$863.85	$863.90