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	$242.85	5.715%	$256.7289	$256.73	$256.75	$256.70
Purchase #2	$77.93	4.400%	$81.3589	$81.36	$81.35	$81.40
Purchase #3	$46.48	7.349%	$49.8958	$49.90	$49.90	$49.90
Purchase #4	$144.31	13.693%	$164.0704	$164.07	$164.05	$164.10
Purchase #5	$226.54	8.510%	$245.8186	$245.82	$245.80	$245.80
Purchase #6	$127.32	11.756%	$142.2877	$142.29	$142.30	$142.30
Purchase #7	$67.77	8.606%	$73.6023	$73.60	$73.60	$73.60
7 purchase totals =	$933.20		$1,013.7626	$1,013.77	$1,013.75	$1,013.80