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	$148.72	3.442%	$153.8389	$153.84	$153.85	$153.80
Purchase #2	$20.46	11.831%	$22.8806	$22.88	$22.90	$22.90
Purchase #3	$117.25	5.611%	$123.8289	$123.83	$123.85	$123.80
Purchase #4	$55.29	9.429%	$60.5033	$60.50	$60.50	$60.50
Purchase #5	$11.77	6.302%	$12.5117	$12.51	$12.50	$12.50
Purchase #6	$180.39	12.800%	$203.4799	$203.48	$203.50	$203.50
Purchase #7	$47.53	9.274%	$51.9379	$51.94	$51.95	$51.90
7 purchase totals =	$581.41		$628.9812	$628.98	$629.05	$628.90