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	$127.25	11.606%	$142.0186	$142.02	$142.00	$142.00
Purchase #2	$89.91	8.840%	$97.858	$97.86	$97.85	$97.90
Purchase #3	$39.43	5.530%	$41.6105	$41.61	$41.60	$41.60
Purchase #4	$230.91	13.469%	$262.0113	$262.01	$262.00	$262.00
Purchase #5	$71.93	8.832%	$78.2829	$78.28	$78.30	$78.30
Purchase #6	$80.27	3.588%	$83.1501	$83.15	$83.15	$83.20
Purchase #7	$120.45	9.115%	$131.429	$131.43	$131.45	$131.40
7 purchase totals =	$760.15		$836.3604	$836.36	$836.35	$836.40