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	$229.33	7.274%	$246.0115	$246.01	$246.00	$246.00
Purchase #2	$138.50	5.327%	$145.8779	$145.88	$145.90	$145.90
Purchase #3	$11.90	10.147%	$13.1075	$13.11	$13.10	$13.10
Purchase #4	$61.41	12.810%	$69.2766	$69.28	$69.30	$69.30
Purchase #5	$85.71	5.449%	$90.3803	$90.38	$90.40	$90.40
Purchase #6	$69.32	3.260%	$71.5798	$71.58	$71.60	$71.60
Purchase #7	$233.65	5.526%	$246.5615	$246.56	$246.55	$246.60
7 purchase totals =	$829.82		$882.7951	$882.80	$882.85	$882.90