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	$190.86	7.842%	$205.8272	$205.83	$205.85	$205.80
Purchase #2	$107.90	10.816%	$119.5705	$119.57	$119.55	$119.60
Purchase #3	$172.61	4.234%	$179.9183	$179.92	$179.90	$179.90
Purchase #4	$160.93	3.863%	$167.1467	$167.15	$167.15	$167.10
Purchase #5	$181.48	9.661%	$199.0128	$199.01	$199.00	$199.00
Purchase #6	$131.69	8.577%	$142.9851	$142.99	$143.00	$143.00
Purchase #7	$75.28	7.779%	$81.136	$81.14	$81.15	$81.10
7 purchase totals =	$1,020.75		$1,095.5966	$1,095.61	$1,095.60	$1,095.50