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	$121.56	4.835%	$127.4374	$127.44	$127.45	$127.40
Purchase #2	$171.42	3.729%	$177.8123	$177.81	$177.80	$177.80
Purchase #3	$225.82	3.427%	$233.5589	$233.56	$233.55	$233.60
Purchase #4	$215.35	4.333%	$224.6811	$224.68	$224.70	$224.70
Purchase #5	$172.53	10.498%	$190.6422	$190.64	$190.65	$190.60
Purchase #6	$40.53	4.786%	$42.4698	$42.47	$42.45	$42.50
Purchase #7	$51.79	3.816%	$53.7663	$53.77	$53.75	$53.80
7 purchase totals =	$999.00		$1,050.3680	$1,050.37	$1,050.35	$1,050.40