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	$114.97	11.306%	$127.9685	$127.97	$127.95	$128.00
Purchase #2	$168.76	8.452%	$183.0236	$183.02	$183.00	$183.00
Purchase #3	$5.67	13.624%	$6.4425	$6.44	$6.45	$6.40
Purchase #4	$118.88	4.139%	$123.8004	$123.80	$123.80	$123.80
Purchase #5	$134.98	13.699%	$153.4709	$153.47	$153.45	$153.50
Purchase #6	$191.71	12.530%	$215.7313	$215.73	$215.75	$215.70
Purchase #7	$90.87	13.858%	$103.4628	$103.46	$103.45	$103.50
7 purchase totals =	$825.84		$913.9000	$913.89	$913.85	$913.90