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	$41.93	3.183%	$43.2646	$43.26	$43.25	$43.30
Purchase #2	$115.45	11.172%	$128.3481	$128.35	$128.35	$128.30
Purchase #3	$235.98	12.522%	$265.5294	$265.53	$265.55	$265.50
Purchase #4	$35.98	5.240%	$37.8654	$37.87	$37.85	$37.90
Purchase #5	$211.91	7.249%	$227.2714	$227.27	$227.25	$227.30
Purchase #6	$213.75	10.711%	$236.6448	$236.64	$236.65	$236.60
Purchase #7	$162.93	13.618%	$185.1178	$185.12	$185.10	$185.10
7 purchase totals =	$1,017.93		$1,124.0415	$1,124.04	$1,124.00	$1,124.00