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	$207.32	9.611%	$227.2455	$227.25	$227.25	$227.20
Purchase #2	$54.45	8.380%	$59.0129	$59.01	$59.00	$59.00
Purchase #3	$159.73	4.222%	$166.4738	$166.47	$166.45	$166.50
Purchase #4	$138.77	7.710%	$149.4692	$149.47	$149.45	$149.50
Purchase #5	$29.67	13.671%	$33.7262	$33.73	$33.75	$33.70
Purchase #6	$195.43	10.865%	$216.6635	$216.66	$216.65	$216.70
Purchase #7	$140.72	7.680%	$151.5273	$151.53	$151.55	$151.50
7 purchase totals =	$926.09		$1,004.1184	$1,004.12	$1,004.10	$1,004.10