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	$196.89	7.563%	$211.7808	$211.78	$211.80	$211.80
Purchase #2	$220.30	10.243%	$242.8653	$242.87	$242.85	$242.90
Purchase #3	$97.39	6.835%	$104.0466	$104.05	$104.05	$104.00
Purchase #4	$104.59	4.523%	$109.3206	$109.32	$109.30	$109.30
Purchase #5	$117.47	6.868%	$125.5378	$125.54	$125.55	$125.50
Purchase #6	$134.49	12.788%	$151.6886	$151.69	$151.70	$151.70
Purchase #7	$87.53	4.706%	$91.6492	$91.65	$91.65	$91.60
7 purchase totals =	$958.66		$1,036.8889	$1,036.90	$1,036.90	$1,036.80