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	$160.27	4.570%	$167.5943	$167.59	$167.60	$167.60
Purchase #2	$56.86	10.791%	$62.9958	$63.00	$63.00	$63.00
Purchase #3	$203.69	13.694%	$231.5833	$231.58	$231.60	$231.60
Purchase #4	$91.85	4.517%	$95.9989	$96.00	$96.00	$96.00
Purchase #5	$168.89	13.355%	$191.4453	$191.45	$191.45	$191.40
Purchase #6	$74.81	10.115%	$82.377	$82.38	$82.40	$82.40
Purchase #7	$163.50	12.275%	$183.5696	$183.57	$183.55	$183.60
7 purchase totals =	$919.87		$1,015.5642	$1,015.57	$1,015.60	$1,015.60