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	$167.96	13.612%	$190.8227	$190.82	$190.80	$190.80
Purchase #2	$99.94	3.418%	$103.3559	$103.36	$103.35	$103.40
Purchase #3	$119.94	9.720%	$131.5982	$131.60	$131.60	$131.60
Purchase #4	$161.76	9.573%	$177.2453	$177.25	$177.25	$177.20
Purchase #5	$228.85	7.672%	$246.4074	$246.41	$246.40	$246.40
Purchase #6	$210.62	13.183%	$238.386	$238.39	$238.40	$238.40
Purchase #7	$6.75	8.410%	$7.3177	$7.32	$7.30	$7.30
7 purchase totals =	$995.82		$1,095.1332	$1,095.15	$1,095.10	$1,095.10