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	$164.30	3.420%	$169.9191	$169.92	$169.90	$169.90
Purchase #2	$80.98	13.516%	$91.9253	$91.93	$91.95	$91.90
Purchase #3	$238.74	7.696%	$257.1134	$257.11	$257.10	$257.10
Purchase #4	$106.90	5.162%	$112.4182	$112.42	$112.40	$112.40
Purchase #5	$189.33	13.839%	$215.5314	$215.53	$215.55	$215.50
Purchase #6	$9.90	10.657%	$10.955	$10.96	$10.95	$11.00
Purchase #7	$127.56	11.781%	$142.5878	$142.59	$142.60	$142.60
7 purchase totals =	$917.71		$1,000.4502	$1,000.46	$1,000.45	$1,000.40