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	$143.73	12.784%	$162.1044	$162.10	$162.10	$162.10
Purchase #2	$57.73	4.729%	$60.4601	$60.46	$60.45	$60.50
Purchase #3	$149.85	4.684%	$156.869	$156.87	$156.85	$156.90
Purchase #4	$248.52	5.357%	$261.8332	$261.83	$261.85	$261.80
Purchase #5	$25.35	4.526%	$26.4973	$26.50	$26.50	$26.50
Purchase #6	$196.37	8.862%	$213.7723	$213.77	$213.75	$213.80
Purchase #7	$180.47	10.746%	$199.8633	$199.86	$199.85	$199.90
7 purchase totals =	$1,002.02		$1,081.3996	$1,081.39	$1,081.35	$1,081.50