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	$98.93	5.707%	$104.5759	$104.58	$104.60	$104.60
Purchase #2	$53.32	11.781%	$59.6016	$59.60	$59.60	$59.60
Purchase #3	$250.83	8.425%	$271.9624	$271.96	$271.95	$272.00
Purchase #4	$154.39	9.301%	$168.7498	$168.75	$168.75	$168.70
Purchase #5	$205.81	8.558%	$223.4232	$223.42	$223.40	$223.40
Purchase #6	$72.59	4.740%	$76.0308	$76.03	$76.05	$76.00
Purchase #7	$129.96	10.237%	$143.264	$143.26	$143.25	$143.30
7 purchase totals =	$965.83		$1,047.6077	$1,047.60	$1,047.60	$1,047.60