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	$70.49	4.301%	$73.5218	$73.52	$73.50	$73.50
Purchase #2	$100.97	12.642%	$113.7346	$113.73	$113.75	$113.70
Purchase #3	$168.72	7.526%	$181.4179	$181.42	$181.40	$181.40
Purchase #4	$127.73	11.186%	$142.0179	$142.02	$142.00	$142.00
Purchase #5	$92.76	6.232%	$98.5408	$98.54	$98.55	$98.50
Purchase #6	$212.74	12.577%	$239.4963	$239.50	$239.50	$239.50
Purchase #7	$46.71	11.807%	$52.225	$52.23	$52.25	$52.20
7 purchase totals =	$820.12		$900.9543	$900.96	$900.95	$900.80