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	$181.26	3.180%	$187.0241	$187.02	$187.00	$187.00
Purchase #2	$126.76	3.618%	$131.3462	$131.35	$131.35	$131.30
Purchase #3	$78.84	9.724%	$86.5064	$86.51	$86.50	$86.50
Purchase #4	$76.38	3.407%	$78.9823	$78.98	$79.00	$79.00
Purchase #5	$82.47	4.299%	$86.0154	$86.02	$86.00	$86.00
Purchase #6	$118.67	4.327%	$123.8049	$123.80	$123.80	$123.80
Purchase #7	$14.57	5.215%	$15.3298	$15.33	$15.35	$15.30
7 purchase totals =	$678.95		$709.0091	$709.01	$709.00	$708.90