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	$110.84	3.190%	$114.3758	$114.38	$114.40	$114.40
Purchase #2	$78.50	6.246%	$83.4031	$83.40	$83.40	$83.40
Purchase #3	$119.28	7.869%	$128.6661	$128.67	$128.65	$128.70
Purchase #4	$89.77	6.204%	$95.3393	$95.34	$95.35	$95.30
Purchase #5	$85.43	6.479%	$90.965	$90.97	$90.95	$91.00
Purchase #6	$10.52	8.127%	$11.375	$11.38	$11.40	$11.40
Purchase #7	$176.74	7.763%	$190.4603	$190.46	$190.45	$190.50
7 purchase totals =	$671.08		$714.5846	$714.60	$714.60	$714.70