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	$23.72	11.553%	$26.4604	$26.46	$26.45	$26.50
Purchase #2	$233.90	4.686%	$244.8606	$244.86	$244.85	$244.90
Purchase #3	$50.60	13.853%	$57.6096	$57.61	$57.60	$57.60
Purchase #4	$98.50	3.282%	$101.7328	$101.73	$101.75	$101.70
Purchase #5	$198.62	12.228%	$222.9073	$222.91	$222.90	$222.90
Purchase #6	$37.71	7.312%	$40.4674	$40.47	$40.45	$40.50
Purchase #7	$205.96	13.488%	$233.7399	$233.74	$233.75	$233.70
7 purchase totals =	$849.01		$927.7780	$927.78	$927.75	$927.80