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	$215.45	13.735%	$245.0421	$245.04	$245.05	$245.00
Purchase #2	$157.72	4.141%	$164.2512	$164.25	$164.25	$164.30
Purchase #3	$175.49	4.658%	$183.6643	$183.66	$183.65	$183.70
Purchase #4	$63.90	13.710%	$72.6607	$72.66	$72.65	$72.70
Purchase #5	$130.25	10.797%	$144.3131	$144.31	$144.30	$144.30
Purchase #6	$151.72	8.576%	$164.7315	$164.73	$164.75	$164.70
Purchase #7	$121.40	3.770%	$125.9768	$125.98	$126.00	$126.00
7 purchase totals =	$1,015.93		$1,100.6397	$1,100.63	$1,100.65	$1,100.70