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	$40.63	12.357%	$45.6506	$45.65	$45.65	$45.70
Purchase #2	$99.92	9.597%	$109.5093	$109.51	$109.50	$109.50
Purchase #3	$127.67	12.265%	$143.3287	$143.33	$143.35	$143.30
Purchase #4	$144.64	13.711%	$164.4716	$164.47	$164.45	$164.50
Purchase #5	$98.55	3.481%	$101.9805	$101.98	$102.00	$102.00
Purchase #6	$174.28	9.415%	$190.6885	$190.69	$190.70	$190.70
Purchase #7	$238.81	11.544%	$266.3782	$266.38	$266.40	$266.40
7 purchase totals =	$924.50		$1,022.0074	$1,022.01	$1,022.05	$1,022.10