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	$174.81	5.568%	$184.5434	$184.54	$184.55	$184.50
Purchase #2	$120.54	4.192%	$125.593	$125.59	$125.60	$125.60
Purchase #3	$92.30	4.676%	$96.6159	$96.62	$96.60	$96.60
Purchase #4	$240.78	13.213%	$272.5943	$272.59	$272.60	$272.60
Purchase #5	$109.25	6.706%	$116.5763	$116.58	$116.60	$116.60
Purchase #6	$35.56	13.256%	$40.2738	$40.27	$40.25	$40.30
Purchase #7	$86.83	7.719%	$93.5324	$93.53	$93.55	$93.50
7 purchase totals =	$860.07		$929.7291	$929.72	$929.75	$929.70