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	$171.32	7.621%	$184.3763	$184.38	$184.40	$184.40
Purchase #2	$128.93	6.261%	$137.0023	$137.00	$137.00	$137.00
Purchase #3	$225.78	3.586%	$233.8765	$233.88	$233.90	$233.90
Purchase #4	$136.27	3.490%	$141.0258	$141.03	$141.05	$141.00
Purchase #5	$78.50	6.126%	$83.3089	$83.31	$83.30	$83.30
Purchase #6	$233.94	3.594%	$242.3478	$242.35	$242.35	$242.30
Purchase #7	$164.95	4.837%	$172.9286	$172.93	$172.95	$172.90
7 purchase totals =	$1,139.69		$1,194.8662	$1,194.88	$1,194.95	$1,194.80