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	$196.41	10.178%	$216.4006	$216.40	$216.40	$216.40
Purchase #2	$210.37	6.735%	$224.5384	$224.54	$224.55	$224.50
Purchase #3	$179.78	10.826%	$199.243	$199.24	$199.25	$199.20
Purchase #4	$231.83	4.686%	$242.6936	$242.69	$242.70	$242.70
Purchase #5	$219.89	8.667%	$238.9479	$238.95	$238.95	$238.90
Purchase #6	$175.75	11.874%	$196.6186	$196.62	$196.60	$196.60
Purchase #7	$21.93	9.691%	$24.0552	$24.06	$24.05	$24.10
7 purchase totals =	$1,235.96		$1,342.4973	$1,342.50	$1,342.50	$1,342.40