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	$138.94	9.308%	$151.8725	$151.87	$151.85	$151.90
Purchase #2	$230.59	4.270%	$240.4362	$240.44	$240.45	$240.40
Purchase #3	$183.34	4.466%	$191.528	$191.53	$191.55	$191.50
Purchase #4	$81.62	7.143%	$87.4501	$87.45	$87.45	$87.50
Purchase #5	$116.38	3.767%	$120.764	$120.76	$120.75	$120.80
Purchase #6	$143.36	10.622%	$158.5877	$158.59	$158.60	$158.60
Purchase #7	$110.66	3.674%	$114.7256	$114.73	$114.75	$114.70
7 purchase totals =	$1,004.89		$1,065.3641	$1,065.37	$1,065.40	$1,065.40