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	$9.76	11.636%	$10.8957	$10.90	$10.90	$10.90
Purchase #2	$164.40	11.750%	$183.717	$183.72	$183.70	$183.70
Purchase #3	$137.84	13.439%	$156.3643	$156.36	$156.35	$156.40
Purchase #4	$160.47	11.670%	$179.1968	$179.20	$179.20	$179.20
Purchase #5	$89.54	7.380%	$96.1481	$96.15	$96.15	$96.10
Purchase #6	$239.63	10.540%	$264.887	$264.89	$264.90	$264.90
Purchase #7	$132.36	10.767%	$146.6112	$146.61	$146.60	$146.60
7 purchase totals =	$934.00		$1,037.8201	$1,037.83	$1,037.80	$1,037.80