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	$166.47	7.321%	$178.6573	$178.66	$178.65	$178.70
Purchase #2	$142.38	6.679%	$151.8896	$151.89	$151.90	$151.90
Purchase #3	$191.47	12.534%	$215.4688	$215.47	$215.45	$215.50
Purchase #4	$179.98	4.783%	$188.5884	$188.59	$188.60	$188.60
Purchase #5	$171.55	6.805%	$183.224	$183.22	$183.20	$183.20
Purchase #6	$181.50	5.159%	$190.8636	$190.86	$190.85	$190.90
Purchase #7	$48.61	5.633%	$51.3482	$51.35	$51.35	$51.30
7 purchase totals =	$1,081.96		$1,160.0399	$1,160.04	$1,160.00	$1,160.10