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	$109.88	4.520%	$114.8466	$114.85	$114.85	$114.80
Purchase #2	$56.32	12.129%	$63.1511	$63.15	$63.15	$63.20
Purchase #3	$227.85	10.741%	$252.3234	$252.32	$252.30	$252.30
Purchase #4	$145.63	11.342%	$162.1474	$162.15	$162.15	$162.10
Purchase #5	$10.73	11.287%	$11.9411	$11.94	$11.95	$11.90
Purchase #6	$99.96	9.466%	$109.4222	$109.42	$109.40	$109.40
Purchase #7	$49.89	3.193%	$51.483	$51.48	$51.50	$51.50
7 purchase totals =	$700.26		$765.3148	$765.31	$765.30	$765.20