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	$110.81	5.595%	$117.0098	$117.01	$117.00	$117.00
Purchase #2	$102.36	8.595%	$111.1578	$111.16	$111.15	$111.20
Purchase #3	$94.59	6.373%	$100.6182	$100.62	$100.60	$100.60
Purchase #4	$100.56	12.368%	$112.9973	$113.00	$113.00	$113.00
Purchase #5	$128.49	11.514%	$143.2843	$143.28	$143.30	$143.30
Purchase #6	$103.41	7.447%	$111.1109	$111.11	$111.10	$111.10
Purchase #7	$167.67	11.391%	$186.7693	$186.77	$186.75	$186.80
7 purchase totals =	$807.89		$882.9476	$882.95	$882.90	$883.00