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	$94.54	8.327%	$102.4123	$102.41	$102.40	$102.40
Purchase #2	$127.69	3.859%	$132.6176	$132.62	$132.60	$132.60
Purchase #3	$97.92	12.222%	$109.8878	$109.89	$109.90	$109.90
Purchase #4	$122.41	4.398%	$127.7936	$127.79	$127.80	$127.80
Purchase #5	$26.67	12.107%	$29.8989	$29.90	$29.90	$29.90
Purchase #6	$27.92	13.680%	$31.7395	$31.74	$31.75	$31.70
Purchase #7	$177.96	10.615%	$196.8505	$196.85	$196.85	$196.90
7 purchase totals =	$675.11		$731.2002	$731.20	$731.20	$731.20