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	$121.62	5.304%	$128.0707	$128.07	$128.05	$128.10
Purchase #2	$215.91	3.644%	$223.7778	$223.78	$223.80	$223.80
Purchase #3	$239.38	4.130%	$249.2664	$249.27	$249.25	$249.30
Purchase #4	$9.55	11.153%	$10.6151	$10.62	$10.60	$10.60
Purchase #5	$199.32	11.506%	$222.2538	$222.25	$222.25	$222.30
Purchase #6	$5.93	11.467%	$6.61	$6.61	$6.60	$6.60
Purchase #7	$203.45	11.684%	$227.2211	$227.22	$227.20	$227.20
7 purchase totals =	$995.16		$1,067.8149	$1,067.82	$1,067.75	$1,067.90