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	$117.46	6.124%	$124.6533	$124.65	$124.65	$124.70
Purchase #2	$92.72	3.383%	$95.8567	$95.86	$95.85	$95.90
Purchase #3	$125.78	5.300%	$132.4463	$132.45	$132.45	$132.40
Purchase #4	$220.49	8.194%	$238.557	$238.56	$238.55	$238.60
Purchase #5	$164.75	8.492%	$178.7406	$178.74	$178.75	$178.70
Purchase #6	$170.65	8.860%	$185.7696	$185.77	$185.75	$185.80
Purchase #7	$104.49	6.835%	$111.6319	$111.63	$111.65	$111.60
7 purchase totals =	$996.34		$1,067.6554	$1,067.66	$1,067.65	$1,067.70