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	$132.40	5.386%	$139.5311	$139.53	$139.55	$139.50
Purchase #2	$140.28	8.583%	$152.3202	$152.32	$152.30	$152.30
Purchase #3	$199.26	7.704%	$214.611	$214.61	$214.60	$214.60
Purchase #4	$187.51	11.509%	$209.0905	$209.09	$209.10	$209.10
Purchase #5	$170.69	8.846%	$185.7892	$185.79	$185.80	$185.80
Purchase #6	$97.52	8.446%	$105.7565	$105.76	$105.75	$105.80
Purchase #7	$38.58	13.435%	$43.7632	$43.76	$43.75	$43.80
7 purchase totals =	$966.24		$1,050.8617	$1,050.86	$1,050.85	$1,050.90