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	$214.89	13.109%	$243.0599	$243.06	$243.05	$243.10
Purchase #2	$36.81	12.455%	$41.3947	$41.39	$41.40	$41.40
Purchase #3	$81.88	6.837%	$87.4781	$87.48	$87.50	$87.50
Purchase #4	$117.78	3.679%	$122.1131	$122.11	$122.10	$122.10
Purchase #5	$237.60	13.229%	$269.0321	$269.03	$269.05	$269.00
Purchase #6	$163.95	13.158%	$185.5225	$185.52	$185.50	$185.50
Purchase #7	$141.67	7.235%	$151.9198	$151.92	$151.90	$151.90
7 purchase totals =	$994.58		$1,100.5202	$1,100.51	$1,100.50	$1,100.50