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	$51.83	8.761%	$56.3708	$56.37	$56.35	$56.40
Purchase #2	$103.68	5.734%	$109.625	$109.63	$109.65	$109.60
Purchase #3	$67.79	5.258%	$71.3544	$71.35	$71.35	$71.40
Purchase #4	$177.45	10.460%	$196.0113	$196.01	$196.00	$196.00
Purchase #5	$68.56	7.284%	$73.5539	$73.55	$73.55	$73.60
Purchase #6	$200.33	10.242%	$220.8478	$220.85	$220.85	$220.80
Purchase #7	$34.70	6.669%	$37.0141	$37.01	$37.00	$37.00
7 purchase totals =	$704.34		$764.7773	$764.77	$764.75	$764.80