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	$89.90	7.372%	$96.5274	$96.53	$96.55	$96.50
Purchase #2	$76.48	10.379%	$84.4179	$84.42	$84.40	$84.40
Purchase #3	$74.45	4.549%	$77.8367	$77.84	$77.85	$77.80
Purchase #4	$174.55	12.773%	$196.8453	$196.85	$196.85	$196.80
Purchase #5	$114.67	7.684%	$123.4812	$123.48	$123.50	$123.50
Purchase #6	$81.92	13.681%	$93.1275	$93.13	$93.15	$93.10
Purchase #7	$246.39	6.140%	$261.5183	$261.52	$261.50	$261.50
7 purchase totals =	$858.36		$933.7543	$933.77	$933.80	$933.60