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	$102.87	3.498%	$106.4684	$106.47	$106.45	$106.50
Purchase #2	$156.31	9.429%	$171.0485	$171.05	$171.05	$171.00
Purchase #3	$127.53	3.123%	$131.5128	$131.51	$131.50	$131.50
Purchase #4	$82.85	10.836%	$91.8276	$91.83	$91.85	$91.80
Purchase #5	$118.30	4.624%	$123.7702	$123.77	$123.75	$123.80
Purchase #6	$108.68	4.312%	$113.3663	$113.37	$113.35	$113.40
Purchase #7	$193.73	7.329%	$207.9285	$207.93	$207.95	$207.90
7 purchase totals =	$890.27		$945.9223	$945.93	$945.90	$945.90